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Posted on Dec 8

OWASP Top 10 2025 Quiz: Week 1 (51 Questions)

#appsec #security #owasp #interview

OWASP Top 10 2025 Quiz: Are You Interview-Ready?

Time to complete: 90-120 minutes

Difficulty: Intermediate to Advanced

Topics: A01 Broken Access Control, A04 Cryptographic Failures, A05 Injection

Why This Matters for Your AppSec Career

If you're interviewing for Application Security Engineer roles you'll face questions about the OWASP Top 10. Not just "What is it?" but deep, practical questions like:

"Why does this code have an IDOR vulnerability?"
"What's wrong with this password hashing implementation?"
"When can ORMs still introduce SQL injection?"

This quiz contains 51 real interview-style questions based on the OWASP Top 10 2025 Release Candidate.

What you'll practice:

🔐 Access control concepts (IDOR, privilege escalation, "deny by default")
🔑 Cryptographic failures (weak algorithms, IV management, KDFs)
💉 Injection vulnerabilities (SQL injection, XSS, context-specific defenses)
🛡️ Prevention techniques actually used in production

After completing this quiz, you'll be able to:

Answer 80%+ of OWASP Top 10 questions in AppSec interviews
Identify access control vulnerabilities in code reviews
Explain cryptographic best practices with confidence
Understand when "safe" libraries can still be misused

How to Use This Quiz

Read each question carefully - many test subtle distinctions
Write down your answers before checking the solutions
Don't peek at answers! The learning happens when you struggle
Check your work at the bottom - detailed explanations included
Track weak areas - questions you miss reveal what to study

Scoring guide:

45-51 correct (88%+): Interview-ready! 🎯
38-44 correct (75-86%): Strong foundation, study weak areas
30-37 correct (59-74%): Good start, review OWASP docs
Below 30 (58%-): Study OWASP Top 10 2025 thoroughly first

The Questions

📋 Section 1: A05 - Injection Fundamentals

Question 1:
According to OWASP Top 10 2025 A05, what is the preferred defense option to prevent injection attacks?

Question 2:
You're reviewing code and see this:

pstmt.setString(1, request.getParameter("acct"));
ResultSet results = pstmt.executeQuery();

The application URL is: https://example.com/app/accountInfo?acct=12345

What vulnerability is this (according to OWASP Top 10 2025 A01 Scenario #1), and how could an attacker exploit it?

Question 5:
OWASP Top 10 2025 A05 states that injection affects 100% of tested applications. It distinguishes between:

Cross-site Scripting (XSS): high frequency / low impact
SQL Injection: low frequency / high impact

Explain why SQL injection has "low frequency" but "high impact" compared to XSS.

Question 10:
OWASP Top 10 2025 A05 mentions that stored procedures can still introduce SQL injection vulnerabilities even when parameterized. Under what condition do stored procedures remain vulnerable?

Question 16:
According to OWASP Top 10 2025 A05, when you cannot use parameterized queries or a safe API, what technique should you use to reduce injection threats?

Question 27:
OWASP Top 10 2025 A05 states that XSS has 30,000+ CVEs while SQL injection has 14,000+ CVEs. Given that XSS has more than double the CVEs, why is SQL injection characterized as "low frequency"?

Question 36:
OWASP Top 10 2025 A05 includes 37 CWEs covering many types of injection beyond SQL injection. Name TWO other types of injection vulnerabilities mentioned in the A05 CWE list.

Question 45:
True or False: "ORMs (like SQLAlchemy, Django ORM) are 100% safe from SQL injection and can never introduce SQL injection vulnerabilities."

If false, explain when ORMs can still be vulnerable.

Question 48:
A developer asks: "I'm using Python's input() function to get user data and then using it in a SQL query with parameterized queries like this:

user_id = input("Enter user ID: ")
cursor.execute("SELECT * FROM users WHERE id = ?", (user_id,))

Is this safe from SQL injection?"

A) Yes, completely safe - parameterized queries prevent all SQL injection

B) No, input() is never safe and allows injection

C) Yes for SQL injection, but there might be other injection risks depending on context

D) No, you need to use an ORM instead

Question 51:
OWASP Top 10 2025 A05 recommends: "Use positive server-side input validation."

What does "positive" validation mean (as opposed to negative validation)? Give an example.

🔐 Section 2: A01 - Broken Access Control Fundamentals

Question 4:
According to OWASP Top 10 2025 A01, why does implementing access control only in the front-end (client-side JavaScript) fail to protect an application? Give a concrete example from the OWASP documentation.

Question 7:
OWASP Top 10 2025 A01 recommends: "Except for public resources, deny by default."

What does this principle mean in practice? Give an example of how this would work in a web application.

Question 9:
An application puts all of their access control in their front-end. An attacker cannot access https://example.com/app/admin_getappInfo due to JavaScript restrictions, but they can execute:

curl https://example.com/app/admin_getappInfo

And successfully retrieve admin information. What is the root cause according to OWASP Top 10 2025 A01 Scenario #3?

Question 11:
Bob is logged in as a regular user. He discovers that by accessing:
https://example.com/admin/deleteUser?userId=500
He can delete user accounts, even though he's not an administrator.

This is an example of:
A) Horizontal privilege escalation (IDOR)

B) Vertical privilege escalation (elevation of privilege)

C) Authentication failure

D) Session hijacking

Question 13:
A user changes the URL parameter from ?userId=123 to ?userId=456 and successfully views another user's private profile data. What is the specific name for this type of vulnerability according to OWASP Top 10 2025 A01?

Question 15:
OWASP Top 10 2025 A01 recommends: "Stateful session identifiers should be invalidated on the server after logout."

Why is server-side invalidation critical? What attack does this prevent?

Question 17:
User Alice (ID=100) accesses her profile: https://example.com/profile?userId=100

She changes the URL to: https://example.com/profile?userId=200 and successfully views Bob's (ID=200) private profile.

This is an example of:
A) Vertical privilege escalation

B) Horizontal privilege escalation (IDOR)

C) Client-side access control bypass

D) Authentication failure

Question 19:
Bob is logged in as a regular user. He discovers that by accessing:
https://example.com/admin/deleteUser?userId=500
He can delete user accounts, even though he's not an administrator.

This is an example of:
A) Horizontal privilege escalation (IDOR)

B) Vertical privilege escalation (elevation of privilege)

C) Authentication failure

D) Session hijacking

Question 21:
According to OWASP Top 10 2025 A01, for stateless JWT tokens, what two security measures are recommended to minimize the window of opportunity for attackers?

Question 22:
According to OWASP Top 10 2025 A01, "Metadata manipulation" is listed as a common access control vulnerability. One specific example given is "replaying or tampering with a JSON Web Token (JWT) access control token." What does "tampering with a JWT" typically involve?

Question 24:
Complete this statement from OWASP Top 10 2025 A01: "CORS misconfiguration allows ____________"

Question 25:
According to OWASP Top 10 2025 A01, what is "force browsing"? Give a concrete example.

Question 28:
According to OWASP Top 10 2025 A01, when should access control failures be logged? And what additional action should be taken when appropriate (e.g., repeated failures)?

Question 31:
According to OWASP Top 10 2025 A01 prevention guidance, why should rate limits be implemented on API and controller access? What specific threat does this mitigate?

Question 33:
Fill in the blanks with the correct terms:

"__________ answers the question 'Who are you?' - it verifies your identity using passwords, tokens, or biometrics.

__________ answers the question 'What can you access?' - it determines your permissions and enforces access control policies like 'deny by default'."

Question 34:
A developer implements access control like this:

@app.route('/api/user/<user_id>/profile')
def get_profile(user_id):
    user = db.query("SELECT * FROM users WHERE id = ?", user_id)
    if user:
        return jsonify(user)
    return "User not found", 404

What critical access control check is missing?

A) Authentication check (is user logged in?)

B) Authorization check (should current user access this user_id?)

C) Input validation (is user_id a valid format?)

D) Rate limiting (prevent automated enumeration)

Question 37:
According to OWASP Top 10 2025 A01 prevention guidance, what should you do about web server directory listing? And what types of files should NOT be present within web roots?

Question 39:
OWASP Top 10 2025 A01 states: "Model access controls should enforce record ownership rather than allowing users to create, read, update, or delete any record."

What does "enforce record ownership at the model level" mean in practice?

Question 40:
According to OWASP Top 10 2025 A01 prevention guidance, which teams should include functional access control testing in their unit and integration tests?

A) Only the security team

B) Only QA engineers

C) Developers and QA staff

D) Only penetration testers

Question 42:
OWASP Top 10 2025 A01 recommends: "Implement access control mechanisms once and reuse them throughout the application."

Why is it better to implement access control ONCE and reuse it, rather than implementing checks separately in each controller/endpoint? Give at least two reasons.

Question 46:
According to OWASP Top 10 2025 A01, one common access control vulnerability is "Violation of the principle of least privilege." Give a concrete code example of violating "least privilege" in an API endpoint.

🔑 Section 3: A04 - Cryptographic Failures

Question 3:
According to OWASP Top 10 2025 A04, the most common CWEs involve weak pseudo-random number generators. Name one of the four specific CWEs mentioned.

Question 6:
According to OWASP Top 10 2025 A04, when using initialization vectors (IVs) in encryption, what is a critical security requirement?

A) The IV must be stored in the same database table as the encrypted data

B) The IV must never be used twice for a fixed key

C) The IV must be exactly 256 bits long

D) The IV must be encrypted before being stored

Question 8:
According to OWASP Top 10 2025 A04, which of the following hash functions are deprecated and should NOT be used?

A) SHA-256 and bcrypt

B) MD5 and SHA1

C) Argon2 and PBKDF2

D) AES-256 and RSA-2048

Question 12:
According to OWASP Top 10 2025 A04, what's the difference between:

Encryption only (e.g., AES in CBC mode)
Authenticated encryption (e.g., AES-GCM)

Why does OWASP recommend authenticated encryption?

Question 14:
According to OWASP Top 10 2025 A04, when converting a password to an encryption key, what must you use?

A) Hash the password with SHA-256

B) Encrypt the password with AES

C) Use a password-based key derivation function (like PBKDF2, bcrypt, Argon2)

D) Store the password in plaintext as the key

Question 18:
True or False: "According to OWASP Top 10 2025 A04, ECB (Electronic Codebook) mode is a secure mode of operation for block ciphers and is recommended for encrypting sensitive data."

If false, why is ECB problematic?

Question 23:
OWASP Top 10 2025 A04 states: "The first thing is to determine the protection needs of data in transit and at rest."

Which types of data require extra protection? Name at least 3 examples from the documentation.

Question 26:
You're storing user passwords in a database. According to OWASP Top 10 2025 A04 cryptographic best practices, which approach should you use?

A) Store passwords in plaintext for easy password recovery

B) Hash passwords with SHA-256

C) Encrypt passwords with AES-256

D) Use adaptive password hashing (bcrypt, Argon2, PBKDF2)

Question 29:
Statement: "According to OWASP Top 10 2025 A04, if you must use an initialization vector (IV) with encryption, the IV needs to be generated with a CSPRNG (cryptographically secure pseudo-random number generator) for ALL cipher modes."

True or False? Explain your answer.

Question 32:
You're conducting a security assessment and discover:

All HTTP traffic is unencrypted (using http:// not https://)
User passwords are transmitted in plaintext
Credit card numbers are sent without encryption

According to OWASP Top 10 2025 A04, what is the first question you should ask when determining protection needs?

Question 35:
According to OWASP Top 10 2025 A04, at which OSI layer should data in transit be encrypted? And what technology is commonly used at this layer for web applications?

Question 38:
According to OWASP Top 10 2025 A04, where should your "most sensitive keys" be stored?

A) In environment variables

B) In a configuration file with restricted permissions

C) In a hardware or cloud-based HSM (Hardware Security Module)

D) Encrypted in the database

Question 41:
You're reviewing code and find this implementation:

import hashlib

def store_password(password):
    hashed = hashlib.sha256(password.encode()).hexdigest()
    db.store(hashed)
    return hashed

According to OWASP Top 10 2025 A04, identify at least TWO problems with this password storage approach.

Question 44:
You're reviewing this code that encrypts user data:

from cryptography.hazmat.primitives.ciphers import Cipher, algorithms, modes
import os

def encrypt_data(plaintext, key):
    iv = os.urandom(16)
    cipher = Cipher(algorithms.AES(key), modes.CBC(iv))
    encryptor = cipher.encryptor()
    ciphertext = encryptor.update(plaintext) + encryptor.finalize()

    db.store(ciphertext)  # IV is NOT stored!

    return ciphertext

According to OWASP Top 10 2025 A04 cryptographic principles, what critical mistake makes this data unrecoverable?

Question 47:
You're conducting a security assessment and discover the following data types:

User email addresses
Marketing preferences (newsletter yes/no)
Credit card numbers (last 4 digits only)
Full credit card numbers with CVV
User's favorite color
Social Security Numbers

According to OWASP Top 10 2025 A04, which of these require extra protection (encryption at rest)? Select all that apply.

🔍 Section 4: Integration & Advanced Topics

Question 20:
You're reviewing this stored procedure for SQL injection vulnerabilities:

CREATE PROCEDURE SearchUsers(@searchTerm varchar(100))
AS
BEGIN
    DECLARE @query varchar(500)
    SET @query = 'SELECT * FROM users WHERE name LIKE ''%' + @searchTerm + '%'''
    EXEC(@query)
END

According to OWASP Top 10 2025 A05, is this vulnerable to SQL injection? If yes, what specific line makes it vulnerable?

Question 30:
You're reviewing this Python Flask code:

@app.route('/delete_user')
def delete_user():
    user_id = request.args.get('user_id')
    query = f"DELETE FROM users WHERE id = {user_id}"
    db.execute(query)
    return "User deleted"

This code has vulnerabilities from BOTH A01 (Broken Access Control) AND A05 (Injection). Identify one vulnerability from each category.

🎯 Check Your Answers

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✅ Answer Key & Explanations

Section 1: A05 - Injection Fundamentals

Answer 1:
Use a safe API that avoids using the interpreter entirely, provides a parameterized interface, or migrates to Object Relational Mapping Tools (ORMs).

Source: OWASP Top 10 2025 A05 - "The preferred option is to use a safe API..."

Answer 2:
Vulnerability: Insecure Direct Object Reference (IDOR) under Broken Access Control

Exploitation: An attacker can modify the acct parameter (e.g., change acct=12345 to acct=67890) to access any user's account information without authorization checks.

Why it's vulnerable: The code checks if the account exists but doesn't verify if the current user should have access to that account.

Source: OWASP Top 10 2025 A01 Scenario #1

Answer 5:
SQL Injection - Low Frequency:

Modern frameworks use ORMs and parameterized queries by default
Developers must explicitly write dangerous raw SQL
SAST tools easily detect SQL concatenation patterns
Result: Harder to introduce accidentally in modern codebases

SQL Injection - High Impact:

Can compromise the entire database in one attack
Dump all passwords, credit cards, personal data
Potential for privilege escalation and OS command execution
Affects ALL users simultaneously

XSS - High Frequency:

Hundreds of potential injection points (search boxes, comments, profiles)
Easy to introduce accidentally (forgot to encode one field)
Context-dependent encoding is complex

XSS - Low Impact (relatively):

Typically affects individual users one at a time
Requires victims to visit the malicious page
Can't directly access the database
More limited attack scope per exploitation

The "frequency" refers to how often vulnerabilities are found in NEW applications being tested, not total historical CVE count.

Answer 10:
Stored procedures are vulnerable when they internally concatenate strings or use dynamic SQL execution (EXECUTE IMMEDIATE in Oracle, exec() in SQL Server).

Example vulnerable stored procedure:

DECLARE @sql varchar(200)
SET @sql = 'SELECT * FROM users WHERE id = ' + @userId  -- Concatenation!
EXEC(@sql)  -- Dynamic execution!

Even if the application calls the stored procedure safely with parameterized queries, the stored procedure itself concatenates user input into SQL strings.

Source: OWASP Top 10 2025 A05

Answer 16:
Use positive server-side input validation. However, this is NOT a complete defense as many applications require special characters.

You can also escape special characters as allowed by the interpreter, but both techniques are error-prone.

Key points:

Positive (whitelist) validation - only allow known good patterns
Server-side - never trust client-side validation
Not complete - applications often need special characters (text areas, APIs)
Error-prone - easy to miss edge cases

Source: OWASP Top 10 2025 A05

Answer 27:
SQL injection has "low frequency" because:

Modern frameworks prevent it by default:
- ORMs (Django, Rails, SQLAlchemy) use parameterized queries
- Developers must explicitly write dangerous raw SQL
SAST tools detect it easily:
- Pattern matching for string concatenation with SQL
- Static analysis catches before deployment
Well-understood defense:
- Parameterized queries are standard practice
- Extensive developer training on this vulnerability

XSS has "high frequency" because:

Hundreds of injection points in typical applications
Context-dependent encoding (HTML, JavaScript, attribute, URL, CSS)
Harder for SAST to detect (depends on template engine settings)

The "frequency" refers to how often found in applications being tested today, not total CVEs across all history.

Answer 36:
Two examples from OWASP Top 10 2025 A05 CWE list:

CWE-79: Cross-Site Scripting (XSS)
CWE-91: XML Injection (Blind XPath Injection)

Section 2: A01 - Broken Access Control Fundamentals

Answer 4:
Client-side access control fails because attackers can bypass browser restrictions entirely by making direct HTTP requests.

OWASP Scenario #3 Example:
An application blocks access to https://example.com/app/admin_getappInfo using JavaScript. The attacker simply runs:

curl https://example.com/app/admin_getappInfo

And successfully retrieves admin information.

Why: Client-side code (JavaScript) runs in the attacker's browser, which they fully control. They can use curl, Postman, Burp Suite, or any HTTP client to bypass frontend restrictions.

Key principle: "Access control is only effective when implemented in trusted server-side code or serverless APIs, where the attacker cannot modify the access control check or metadata."

Source: OWASP Top 10 2025 A01 Scenario #3

Answer 7:
"Deny by default" means: All resources are inaccessible by default unless explicitly granted permission.

Example:

# ✅ GOOD - Deny by default
def get_user_data(user_id, current_user):
    # Default: DENY
    if current_user.id != user_id and not current_user.is_admin:
        return "Access denied"  # Denied by default!
    return database.get_user(user_id)

# ❌ BAD - Allow by default
def get_user_data(user_id):
    # Default: ALLOW (unless explicitly blocked)
    if user_id in BLOCKED_USERS:
        return "Access denied"
    return database.get_user(user_id)  # Anyone can access!

In practice:

Public blog posts → Explicitly marked as public
User profiles → Denied by default, only accessible if you own it OR are admin
Admin dashboard → Denied by default, only accessible with explicit admin role grant

Source: OWASP Top 10 2025 A01

Answer 9:
Root cause: Access control is only implemented on the client-side (front-end) instead of the server-side.

The server serves the admin page to anyone who requests it - only the JavaScript tries to block it. When the attacker bypasses the browser (using curl), there's no server-side check to prevent access.

Prevention: "Access control is only effective when implemented in trusted server-side code or serverless APIs, where the attacker cannot modify the access control check or metadata."

Source: OWASP Top 10 2025 A01 Scenario #3

Answer 11:
B) Vertical privilege escalation (elevation of privilege)

Bob is a regular user (lower privilege) accessing admin functionality (delete users - higher privilege). He's elevating from user → admin capabilities, which is vertical movement up the privilege hierarchy.

From OWASP A01: "Elevation of privilege. Acting as a user without being logged in or acting as an admin when logged in as a user."

Not horizontal: Would be if Bob (user) accessed Alice's (user) profile - same privilege level.

Source: OWASP Top 10 2025 A01

Answer 13:
IDOR (Insecure Direct Object Reference)

This is the specific vulnerability name when users can manipulate object identifiers (like userId) to access other users' resources.

Also correct (but more general): Horizontal privilege escalation - accessing other users' data at the same privilege level.

OWASP states: "Permitting viewing or editing someone else's account by providing its unique identifier (insecure direct object references)"

Source: OWASP Top 10 2025 A01

Answer 15:
Server-side invalidation prevents session replay attacks and session hijacking.

Why it's critical:
Without server-side invalidation, even after a user logs out, the session token remains valid. If an attacker stole the token (via XSS, network sniffing, etc.), they can continue using it to impersonate the victim.

Example:

User logs out at coffee shop
Attacker captured session cookie earlier
Without server-side invalidation: Attacker can still access the account
With server-side invalidation: Token is marked invalid, attack fails

Client-side only (insecure):

document.cookie = "sessionId=; expires=Thu, 01 Jan 1970"  // ❌ Token still valid on server!

Server-side (secure):

sessions.delete(session_id)  # ✓ Server marks session invalid

Source: OWASP Top 10 2025 A01

Answer 17:
B) Horizontal privilege escalation (IDOR)

Alice and Bob are same privilege level (both regular users). Alice accesses Bob's data by manipulating the identifier (userId parameter). This is horizontal movement across same privilege level.

From OWASP: "Permitting viewing or editing someone else's account by providing its unique identifier (insecure direct object references)"

Source: OWASP Top 10 2025 A01

Answer 19:
B) Vertical privilege escalation (elevation of privilege)

Bob is a regular user accessing admin-level functionality (delete users), which is elevation to higher privilege.

From OWASP: "Elevation of privilege. Acting as a user without being logged in or acting as an admin when logged in as a user."

Source: OWASP Top 10 2025 A01

Answer 21:
Two security measures:

JWT tokens should be short-lived (e.g., 15-minute expiration) to minimize the window of opportunity if stolen
For longer-lived JWTs, follow OAuth standards to revoke access (implement server-side revocation capability)

Why both are needed:

Short-lived: Natural expiration limits damage
Revocation: Manual invalidation when needed (logout, password change, suspicious activity)

Source: OWASP Top 10 2025 A01

Answer 22:
JWT tampering involves modifying claims in the JWT payload to escalate privileges.

Example:
Original JWT payload:

{
  "userId": "123",
  "role": "user",
  "exp": 1234567890
}

Attacker tampers to:

{
  "userId": "123",
  "role": "admin",  ← Changed!
  "exp": 9999999999  ← Extended!
}

If the JWT signature isn't properly verified, the attacker gains admin access.

Source: OWASP Top 10 2025 A01

Answer 24:
"CORS misconfiguration allows API access from unauthorized or untrusted origins."

Key term: "origins" (not regions) - refers to web security concept (scheme + host + port)

Example origins:

https://example.com:443
https://attacker.com:443

Attack scenario:

// Attacker's site: https://evil.com
fetch('https://yourbank.com/api/accounts', {
  credentials: 'include'  // Sends victim's cookies!
})

If CORS allows https://evil.com, attacker can steal data.

Source: OWASP Top 10 2025 A01

Answer 25:
Force browsing is guessing URLs to access authenticated pages as an unauthenticated user, or privileged pages as a standard user.

Examples:

Unauthenticated access:

User (not logged in) tries:
https://example.com/app/dashboard
https://example.com/app/settings

Privilege escalation:

Regular user tries:
https://example.com/admin/users
https://example.com/admin/deleteUser

It's called "force" browsing because attackers "force" their way by guessing/enumerating URLs using tools like DirBuster or Gobuster.

Source: OWASP Top 10 2025 A01

Answer 28:
Log access control failures: Always (every time a failure occurs)

Alert admins when appropriate: For repeated failures, patterns suggesting reconnaissance, or privilege escalation attempts

Example alert scenario:

User ID 12345 attempted to access:
- /admin/users (failed) - 10:01 AM
- /admin/delete (failed) - 10:01 AM  
- /admin/logs (failed) - 10:02 AM
🚨 Alert: Possible privilege escalation attack!

Why both matter:

Logs provide audit trail for incident response
Alerts enable real-time response to active attacks

Source: OWASP Top 10 2025 A01

Answer 31:
Why implement rate limits: To minimize the harm from automated attack tooling

Threats mitigated:

Brute force attacks: Password guessing, credential stuffing
Enumeration attacks: Discovering valid usernames, user IDs
DoS prevention: Resource exhaustion from automated requests

Example:
Without rate limiting:

Attacker tries 10,000 passwords/second
Finds valid password in minutes

With rate limiting (5 requests/minute):

Attacker limited to 5 attempts/minute
Would take 33+ hours for 10,000 attempts
Attack becomes impractical

Source: OWASP Top 10 2025 A01

Answer 33:
"Authentication answers the question 'Who are you?' - it verifies your identity using passwords, tokens, or biometrics.

Authorization answers the question 'What can you access?' - it determines your permissions and enforces access control policies like 'deny by default'."

Examples:

Authentication: Login with username/password
Authorization: Regular user can't access /admin/dashboard

Source: OWASP Top 10 2025 A01 (concept throughout)

Answer 34:
B) Authorization check (should current user access this user_id?)

The missing check:

# Authorization check needed!
if current_user.id != user_id and not current_user.is_admin:
    return "Access Denied", 403

The code checks if the user exists but doesn't verify if the current user should have access to that specific user_id. This is an IDOR vulnerability - anyone can access any user's profile by changing the user_id parameter.

From OWASP: "Model access controls should enforce record ownership rather than allowing users to create, read, update, or delete any record."

Source: OWASP Top 10 2025 A01

Answer 37:
Three security measures:

Disable web server directory listing
Ensure file metadata (e.g., .git) is not present within web roots
Ensure backup files are not present within web roots

Why this matters:

Directory listing enabled:

https://example.com/uploads/
  - secret_passwords.txt  ← Attacker sees all files!
  - database_backup.sql

File metadata exposed:

https://example.com/.git/config  ← Attacker downloads source code!

Backup files exposed:

https://example.com/config.php.bak  ← Attacker gets credentials!

Source: OWASP Top 10 2025 A01

Answer 39:
"Enforce record ownership at the model level" means building authorization checks into the data access layer, not just controllers.

❌ Controller level only (easy to forget):

@app.route('/posts/<post_id>')
def get_post(post_id):
    # Might forget to check ownership!
    post = Post.query.get(post_id)
    return jsonify(post)

✅ Model level enforcement (automatic):

# Model with built-in ownership check
class Post(db.Model):
    @classmethod
    def get_for_user(cls, post_id, user_id):
        # Ownership check built into model!
        return cls.query.filter_by(
            id=post_id, 
            owner_id=user_id
        ).first()

# Controller - ownership automatically enforced
@app.route('/posts/<post_id>')
def get_post(post_id):
    post = Post.get_for_user(post_id, current_user.id)
    if not post:
        return "Not found", 404
    return jsonify(post)

Key principle: Ownership is built into data access patterns, impossible to forget.

Source: OWASP Top 10 2025 A01

Answer 40:
C) Developers and QA staff

Why both:

Developers:

Write unit tests as they code
Understand business logic and edge cases
Find bugs early (100x cheaper to fix)

QA:

Write integration tests before release
Know user workflows
Test complete authorization scenarios

Why not just security team:

Security team can't scale to review all features
Developers ship 50-100 features/week
Need distributed ownership for shift-left security

Source: OWASP Top 10 2025 A01

Answer 42:
Two reasons:

1. Consistency (reduced errors):

100 endpoints × separate checks = 100 chances to make mistakes
1 centralized mechanism × reuse = 1 place to get right
Human error is inevitable - minimize attack surface

2. Maintainability:

Business rule changes: Update 1 decorator vs 50 different files
Security patches: Fix vulnerability once, applies everywhere
Auditing: Review 1 implementation, not 100

Example:

# ✅ Centralized (reusable)
@require_ownership('post')
def get_post(id):
    return post

@require_ownership('comment')
def get_comment(id):  # Can't forget - obvious it's needed!
    return comment

Source: OWASP Top 10 2025 A01

Answer 46:
Example code violating least privilege:

# ❌ Violates Least Privilege
@app.route('/api/users/<user_id>/profile')
def get_profile(user_id):
    # No access control - ANYONE can access ANY profile!
    user = User.query.get(user_id)
    return jsonify(user)

Correct implementation:

# ✅ Follows Least Privilege
@app.route('/api/users/<user_id>/profile')
@login_required
def get_profile(user_id):
    # Access granted only to owner or admin
    if current_user.id != user_id and not current_user.is_admin:
        return "Access Denied", 403

    user = User.query.get(user_id)
    return jsonify(user)

Source: OWASP Top 10 2025 A01

Section 3: A04 - Cryptographic Failures

Answer 3:
Any ONE of these four CWEs:

CWE-327: Use of a Broken or Risky Cryptographic Algorithm
CWE-331: Insufficient Entropy
CWE-1241: Use of Predictable Algorithm in Random Number Generator
CWE-338: Use of Cryptographically Weak Pseudo-Random Number Generator (PRNG)

Source: OWASP Top 10 2025 A04

Answer 6:
B) The IV must never be used twice for a fixed key

From OWASP: "In all cases, the IV should never be used twice for a fixed key."

Why this matters:

Reusing an IV with the same key can reveal patterns in encrypted data
In some cipher modes (like CTR), IV reuse completely breaks encryption
This is a common real-world vulnerability ("nonce reuse" attacks)

Source: OWASP Top 10 2025 A04

Answer 8:
B) MD5 and SHA1

From OWASP: "Are deprecated hash functions such as MD5 or SHA1 in use?"

Why they're deprecated:

MD5: Collision attacks proven since 2004
SHA1: Collision attacks proven since 2017 (Google demonstrated practical attack)

What to use instead:

SHA-256, SHA-384, SHA-512 (SHA-2 family)
SHA-3
For passwords: bcrypt, Argon2, PBKDF2

Source: OWASP Top 10 2025 A04

Answer 12:
Encryption only (e.g., AES-CBC):

Provides confidentiality (can't read the message)
Does NOT provide integrity (can't detect tampering)
Vulnerable to padding oracle attacks, bit-flipping

Authenticated encryption (e.g., AES-GCM):

Provides confidentiality (can't read the message)
Provides integrity (detects tampering via MAC/authentication tag)
Provides authenticity (proves sender had the key)

Why OWASP recommends authenticated encryption:
Without it, attackers can modify ciphertext undetected. For example, modifying encrypted credit card data in transit. Authenticated encryption detects and rejects any modifications.

Source: OWASP Top 10 2025 A04

Answer 14:
C) Use a password-based key derivation function (like PBKDF2, bcrypt, Argon2)

From OWASP: "If a password is used, then it must be converted to a key via an appropriate password base key derivation function."

Why:

Direct password: Weak (short, low entropy)
SHA-256 hash: Too fast, vulnerable to brute-force
KDF (PBKDF2/Argon2): Intentionally slow, salted, stretches weak passwords into strong keys

Source: OWASP Top 10 2025 A04

Answer 18:
FALSE

Why ECB is problematic:

Deterministic: Same plaintext → same ciphertext (reveals patterns)
Statistical analysis vulnerability: Famous "ECB penguin" example where image patterns remain visible after encryption
Block replacement attacks: Attacker can swap encrypted blocks

From OWASP: "Is an insecure mode of operation such as ECB in use?"

Better alternatives:

CBC mode with random IV
CTR mode with unique nonce
GCM mode (provides AEAD - authenticated encryption)

Source: OWASP Top 10 2025 A04

Answer 23:
Data requiring extra protection (any 3):

Passwords
Credit card numbers
Health records
Personal information (including email addresses under GDPR)
Business secrets

From OWASP: "For example, passwords, credit card numbers, health records, personal information, and business secrets require extra protection, mainly if that data falls under privacy laws, e.g., EU's General Data Protection Regulation (GDPR), or regulations, e.g., financial data protection such as PCI Data Security Standard (PCI DSS)."

Source: OWASP Top 10 2025 A04

Answer 26:
D) Use adaptive password hashing (bcrypt, Argon2, PBKDF2)

Why:

Adaptive hashing = intentionally slow, configurable work factor
As computers get faster, increase iterations/cost
Built-in salt prevents rainbow table attacks
Protects against brute-force

Why other options fail:

A (Plaintext): Catastrophic - immediate compromise if breached
B (SHA-256): Too fast - billions of hashes/second on GPU
C (AES-256): Reversible - if key is compromised, all passwords exposed

Source: OWASP Top 10 2025 A04 best practices

Answer 29:
FALSE

From OWASP: "For many modes, this means using a CSPRNG (cryptographically secure pseudo random number generator). For modes that require a nonce, then the initialization vector (IV) does not need a CSPRNG."

The distinction:

Modes requiring CSPRNG (random IV):

CBC mode - IV must be unpredictable
CFB mode - IV must be random

Modes requiring only a NONCE (unique value):

CTR mode - Just needs unique nonce (can be counter: 1, 2, 3...)
GCM mode - Nonce can be sequential

Critical for ALL modes: Never reuse IV/nonce with the same key

Source: OWASP Top 10 2025 A04

Answer 32:
The first question to ask: "Is any data transmitted in clear text?"

From OWASP: "The first thing is to determine the protection needs of data in transit and at rest. For example, passwords, credit card numbers, health records, personal information, and business secrets require extra protection... For all such data: Is any data transmitted in clear text?"

The assessment flow:

First: Identify what data exists and its sensitivity (data classification)
Then: Ask technical questions about encryption, algorithms, etc.

Source: OWASP Top 10 2025 A04

Answer 35:
OSI Layer 4 (Transport Layer) according to OWASP documentation

Technology: TLS/SSL (Transport Layer Security)

From OWASP: "Generally speaking, all data in transit should be encrypted at the transport layer (OSI layer 4)."

Technical note: There's debate about TLS placement - it technically operates between TCP (Layer 4) and HTTP (Layer 7), spanning Session/Presentation layers (5-6). OWASP uses "Layer 4" as industry shorthand.

Source: OWASP Top 10 2025 A04

Answer 38:
C) In a hardware or cloud-based HSM (Hardware Security Module)

From OWASP: "Store your most sensitive keys in a hardware or cloud-based HSM."

Why HSM:

Dedicated tamper-resistant hardware
Keys never leave the device
FIPS 140-2/3 certified
Physical security protections

Cloud-based HSM examples:

AWS CloudHSM / AWS KMS
Azure Key Vault (Premium tier)
Google Cloud KMS / Cloud HSM

Source: OWASP Top 10 2025 A04

Answer 41:
Two problems:

1. Not using a password-based key derivation function (KDF):

SHA-256 is too fast (~2 billion hashes/second on GPU)
Brute force attacks are trivial
No work factor/cost parameter
Should use bcrypt, Argon2, or PBKDF2

2. No salt:

Same password → same hash
Rainbow table attacks work
Attacker can crack all instances of "password123" at once

Example attack:

User1: password123 → 9af15b336e...
User2: password123 → 9af15b336e...  ← Same hash!

Source: OWASP Top 10 2025 A04

Answer 44:
The IV is not stored!

CBC mode decryption requires the exact same IV used during encryption. Without storing the IV alongside the ciphertext, the data becomes permanently unrecoverable.

Decryption requires:

plaintext = decrypt(ciphertext, key, iv)
                                    ^^
                          Need the original IV!

Secure implementation:

# Store BOTH ciphertext AND IV
db.store({
    'ciphertext': ciphertext,
    'iv': iv  # ✓ Must store IV!
})

Note: The IV doesn't need to be secret, but it MUST be unique per encryption and available for decryption.

Source: OWASP Top 10 2025 A04 cryptographic principles

Answer 47:
Require extra protection (encryption at rest):

✅ User email addresses (Personal information under GDPR)
✅ Full credit card numbers with CVV (PCI DSS regulated)
✅ Social Security Numbers (PII)

Do NOT require extra protection:

❌ Marketing preferences (Not sensitive)
❌ Credit card last 4 digits only (Masked/truncated - PCI DSS allows)
❌ Favorite color (Not sensitive)

From OWASP: "passwords, credit card numbers, health records, personal information, and business secrets require extra protection, mainly if that data falls under privacy laws, e.g., EU's General Data Protection Regulation (GDPR)"

Source: OWASP Top 10 2025 A04

Section 4: Integration & Advanced Topics

Answer 20:
Yes, vulnerable to SQL injection.

Vulnerable line: SET @query = 'SELECT * FROM users WHERE name LIKE ''%' + @searchTerm + '%'''

The problem: String concatenation (+ @searchTerm +) embeds user input directly into the SQL string. An attacker can inject:

searchTerm = "'; DROP TABLE users; --"
Result: SELECT * FROM users WHERE name LIKE '%'; DROP TABLE users; --%'

From OWASP: "Even when parameterized, stored procedures can still introduce SQL injection if PL/SQL or T-SQL concatenates queries and data or executes hostile data with EXECUTE IMMEDIATE or exec()."

The EXEC(@query) then executes this malicious SQL.

Source: OWASP Top 10 2025 A05

Answer 30:
A01 (Broken Access Control) vulnerabilities:

No authentication check - anyone can call the endpoint
No authorization check - no verification of permissions
IDOR vulnerability - direct manipulation of user_id parameter
Missing "deny by default" - endpoint is wide open

A05 (Injection) vulnerability:

SQL Injection in the line: query = f"DELETE FROM users WHERE id = {user_id}"
F-string concatenation directly embeds user input
Attack: /delete_user?user_id=1; DROP TABLE users; --

Secure version:

@app.route('/delete_user')
@login_required  # Authentication
def delete_user():
    user_id = request.args.get('user_id')

    # Authorization check
    if not current_user.is_admin:
        return "Access Denied", 403

    # Parameterized query
    query = "DELETE FROM users WHERE id = ?"
    db.execute(query, (user_id,))
    return "User deleted"

Sources: OWASP Top 10 2025 A01 & A05

🎯 Your Score

Count your correct answers and see where you stand:

45-51 correct (88%+): 🔥 Interview-ready! You have strong OWASP Top 10 knowledge
38-44 correct (75-86%): 💪 Solid foundation - study your weak areas
30-37 correct (59-74%): 📚 Good start - review OWASP 2025 documentation
Below 30 (58%-): 📖 Study OWASP Top 10 2025 thoroughly, then retake

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📚 Additional Resources

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OWASP Top 10 2025 RC1
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Tags: #appsec #security #owasp #cybersecurity #infosec #webappsec #hacking #bugbounty #pentesting #interview

This quiz is based on the OWASP Top 10 2025 Release Candidate. All questions reference official OWASP documentation.

DEV Community

OWASP Top 10 2025 Quiz: Week 1 (51 Questions)

OWASP Top 10 2025 Quiz: Are You Interview-Ready?

Why This Matters for Your AppSec Career

How to Use This Quiz

The Questions

📋 Section 1: A05 - Injection Fundamentals

🔐 Section 2: A01 - Broken Access Control Fundamentals

🔑 Section 3: A04 - Cryptographic Failures

🔍 Section 4: Integration & Advanced Topics

🎯 Check Your Answers

✅ Answer Key & Explanations

Section 1: A05 - Injection Fundamentals

Section 2: A01 - Broken Access Control Fundamentals

Section 3: A04 - Cryptographic Failures

Section 4: Integration & Advanced Topics

🎯 Your Score

🚀 Level Up Your AppSec Skills

📚 Additional Resources

💬 Let's Connect

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