Authentication is one of the most important parts of any web application. A single mistake in a login system can expose user accounts, leak sensitive information, or even allow attackers to gain complete access to an application.
Unfortunately, many developers learn secure authentication only after discovering security issues in production.
To help developers and security students understand these risks, I created Vulnerable Login, a deliberately insecure login application that contains 12 common authentication vulnerabilities found in real-world web applications.
This project is built for education only. It allows developers and penetration testers to safely explore insecure authentication mechanisms and understand how to fix them.
Why I Built Vulnerable Login
Many tutorials explain authentication using only secure examples. While that is important, it doesn't show developers what insecure authentication actually looks like.
Understanding vulnerable code helps developers:
- Identify authentication weaknesses before attackers do
- Learn common security mistakes
- Practice web application penetration testing
- Improve secure coding skills
- Understand how authentication attacks work
The goal of this project is to make learning authentication security practical instead of theoretical.
Live Demo
You can test the vulnerable application here:
Live Demo: https://yogsec.github.io/Vulnerable-Login
GitHub Repository:
https://github.com/yogsec/Vulnerable-Login
Important: Never use this code in production. Every vulnerability is intentionally included for educational purposes.
Authentication Vulnerabilities Included
The project contains twelve intentionally vulnerable authentication mechanisms.
1. SQL Injection Authentication Bypass
User input is directly inserted into SQL queries.
Developers will learn:
- Why parameterized queries are important
- How SQL Injection bypasses authentication
- How prepared statements prevent attacks
2. Plaintext Password Storage
Passwords are stored in plain text instead of being securely hashed.
This demonstrates why passwords should never be stored without strong hashing algorithms such as bcrypt or Argon2.
3. No Rate Limiting
The login page allows unlimited login attempts.
Students can understand how brute-force attacks become possible when no request limits exist.
4. No Account Lockout
Even after repeated failed login attempts, accounts remain accessible.
This demonstrates why account lockout policies are an important security control.
5. Weak Passwords
The application contains users with predictable passwords.
Examples include passwords that attackers commonly try first during password guessing attacks.
6. Weak MD5 Password Hashing
Passwords are hashed using MD5 without salt.
Developers can understand why MD5 is no longer considered secure for password storage.
7. Verbose Error Messages
Different error messages reveal whether a username exists.
This small mistake provides valuable information to attackers.
8. User Enumeration
The application allows attackers to determine valid usernames.
Developers can learn how consistent responses reduce information disclosure.
9. Session Fixation
The session identifier is not regenerated after successful login.
Students can observe how attackers may hijack authenticated sessions.
10. Hardcoded Credentials
Administrative credentials are embedded directly inside the source code.
This demonstrates why secrets should never be committed into repositories.
11. No HTTPS Protection
Credentials are transmitted over HTTP instead of HTTPS.
Developers can understand why encrypted communication is essential for protecting usernames and passwords.
12. CSRF Protection That Doesn't Work
The application includes an anti-CSRF token but never validates it.
This demonstrates how incomplete security implementations create a false sense of protection.
Who Should Use This Project?
This repository is useful for:
- Frontend Developers
- Backend Developers
- Full Stack Developers
- Security Researchers
- Bug Bounty Hunters
- Penetration Testers
- Students Learning Cybersecurity
- Web Security Trainers
- University Instructors
What Developers Will Learn
After exploring this project, you'll better understand:
- Authentication security
- Login security best practices
- Password storage
- Session management
- Secure authentication design
- Brute-force protection
- SQL Injection prevention
- CSRF mitigation
- User enumeration prevention
- Secure coding practices
These concepts are directly applicable when building secure web applications.
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