The OWASP Top 10 is the security industry’s short list of the risks most likely to get a web application breached, and it is the first place I send any developer who asks where to start. This guide walks the categories that cause the most damage—in plain language, with the single most important fix for each. It is written for developers who ship features, not for auditors.
Quick answer: The OWASP Top 10 is a free, community-built list of the ten most critical web application security risks. Treat it as a prioritized checklist—lock down access control, injection, and misconfiguration first, because that is where most real breaches begin.
What the OWASP Top 10 is
The OWASP Top 10 is a consensus document from the Open Worldwide Application Security Project, a nonprofit that publishes free, vendor-neutral security guidance. It is rebuilt every few years from real breach data, and the 2021 edition is the one most teams still reference in 2026. Each entry is a category of risk, not a single bug—so “Injection” covers SQL, command, and template injection at once.
A few things are worth being clear about up front:
It is an awareness and prioritization tool.
It is ranked by real-world prevalence and impact.
It is not a complete checklist; clearing it does not make an app “secure.”
It is not a certification, though many standards reference it.
Broken access control
Broken access control tops the current OWASP Top 10 because it is both common and immediately damaging. It means the app lets someone do something their role should not allow—reading another customer’s invoice by changing an ID in the URL, or calling an admin endpoint from a normal account.
The root cause is trusting the client: if the browser can send a request, assume an attacker can send the same one with any values. Enforce authorization on the server for every request, deny by default, and confirm the user owns the specific object being touched—not merely that they are logged in.
Cryptographic failures
Cryptographic failures—once called “sensitive data exposure”—are what happen when data that should be protected is not: login pages served over plain HTTP, passwords stored with a fast or unsalted hash, API keys committed to source control, or broken algorithms like MD5 used for security-sensitive work.
The fixes are unglamorous and effective: force HTTPS everywhere, encrypt sensitive data at rest, keep secrets out of your repository, and hash passwords with argon2 or bcrypt rather than a general-purpose digest.
Injection
Injection is the category that made the OWASP Top 10 famous, and it still earns its place. It happens when untrusted input is mixed directly into a command an interpreter runs—a SQL query, a shell command, or an HTML page—so the interpreter cannot tell your code from the attacker’s data and runs both.
The two you will meet most are SQL injection and cross-site scripting, and the defense is the same idea: keep data and code in separate lanes with parameterized queries and output encoding. We go deep in SQL Injection Explained and Cross-Site Scripting Explained.
Insecure design
Insecure design is different from the rest of the list: it is about flaws in the plan, not the code. A perfectly implemented feature can still be insecure if the design never accounted for abuse—a password reset with no rate limit, or a checkout that trusts a price sent by the browser.
You cannot patch your way out of a design flaw; you have to redesign. Add lightweight threat modeling early—ask how someone could abuse each feature—and write abuse cases next to your user stories so the guardrails are part of the spec.
Security misconfiguration
Security misconfiguration covers the settings you forgot rather than the code you wrote: default admin passwords, error pages that leak stack traces, an unsecured storage bucket, debug mode left on in production, or permissive CORS that lets any site call your API.
Because these are settings, the fix is process rather than cleverness. Ship a hardened, repeatable configuration, disable features you do not use, and scan configuration in your pipeline so problems are caught before a user sees them.
Vulnerable dependencies
Modern apps are mostly other people’s code, so vulnerable and outdated components are a permanent fixture on the OWASP Top 10. One known flaw in a popular library—the kind that earns a CVE and a headline—can expose every app that ships it, however careful your own code is.
The fix is boring and it works: keep an inventory of what you depend on, scan it automatically, update on a schedule instead of in a panic, and treat a high-severity alert in a production dependency as a real bug.
Auth failures
Identification and authentication failures cover the ways login itself breaks: accepting weak or already-breached passwords, sessions that never expire, unlimited credential-stuffing attempts, or passwords stored so poorly that a database leak becomes account takeover.
Lean on proven building blocks instead of rolling your own. Use a well-reviewed framework or identity provider, store passwords with a strong hash, add multi-factor authentication for anything sensitive, and rate-limit login attempts.
How to use this list on your own app
The point of the OWASP Top 10 is not to read it once but to turn it into a review pass. Walk your app against each category and note where you have a real control and where you are guessing. The table below pairs each risk with the first fix I would reach for.
| Risk | First fix to reach for |
|---|---|
| Broken access control | Enforce authorization server-side; deny by default |
| Cryptographic failures | Force HTTPS; hash passwords with argon2 or bcrypt |
| Injection | Parameterized queries and output encoding |
| Insecure design | Threat-model features; write abuse cases |
| Security misconfiguration | Harden defaults; scan config in CI |
| Vulnerable dependencies | Inventory and auto-scan; patch on a schedule |
| Authentication failures | Use a vetted auth library; add MFA and rate limits |
Do not try to fix everything at once. Rank the gaps by how exposed and how damaging each one is, fix the worst first, and add a test so it cannot quietly return.
Frequently asked questions
Is the OWASP Top 10 a security standard I must comply with?
No—it is an awareness document, not a pass-or-fail certification. Several formal standards do reference it, so covering the Top 10 is a strong baseline that usually overlaps with compliance work you already need to do.
How often is the OWASP Top 10 updated?
Roughly every three to four years, from fresh vulnerability data and a practitioner survey. The 2021 edition is the current widely referenced version, and categories tend to merge and re-rank over time. Check owasp.org for the latest edition.
Does clearing the OWASP Top 10 mean my app is secure?
No, and it is risky to treat it that way. The list is deliberately short and skips many vulnerability classes, so use it as a floor—then add testing, code review, and, for high-stakes systems, a professional audit.
Is the OWASP Top 10 only for web applications?
The flagship list targets web apps, but OWASP also publishes companion lists for APIs, mobile, and large language model apps. If you work in one of those areas, read the matching list too—the mindset carries over.
None of the OWASP Top 10 needs a security background to address—each one is a habit you build into how you write and review code. Pick the two categories closest to what you are shipping this week, apply the first fix from the table, and add a test that proves it. From there, the deep-dive guides on injection, passwords, and tokens take you the rest of the way.
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Originally published on **Fortify* — Application security, explained for the developers who ship the code.*
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