Introduction to Web Security

Web security refers to protecting websites and web applications from attacks, unauthorized access, and data breaches. As a web developer, understanding security is not optional — vulnerabilities in your code can lead to stolen data, defaced websites, and serious legal consequences.

The OWASP (Open Web Application Security Project) maintains a list of the top 10 most critical web application security risks.

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# Common web vulnerabilities to avoid:

1. SQL Injection
   - Never concatenate user input into SQL
   - Use parameterized queries / prepared statements

2. Cross-Site Scripting (XSS)
   - Never inject unescaped user data into HTML
   - Use context-aware escaping (htmlspecialchars in PHP)

3. CSRF (Cross-Site Request Forgery)
   - Use CSRF tokens for all state-changing requests
   - Validate the Origin/Referer header

4. Insecure Direct Object References
   - Always verify authorization before accessing resources
   - Don't expose internal IDs directly

5. Sensitive Data Exposure
   - Always use HTTPS
   - Never store passwords in plaintext (use bcrypt/argon2)
   - Never commit secrets to version control

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Related Resources

Web Security Reference

Complete tag & property list

Web Security How-To Guides

Step-by-step practical guides

Web Security Exercises

Practice what you've learned