Security is not optional—it's a fundamental aspect of building trustworthy web applications. Understanding common vulnerabilities and best practices is essential for every developer.

Common Vulnerabilities

SQL Injection

SQL injection occurs when user input is directly concatenated into SQL queries, allowing attackers to execute malicious SQL code.

Prevention: Use parameterized queries or ORMs that handle escaping automatically.

Cross-Site Scripting (XSS)

XSS attacks inject malicious scripts into web pages viewed by other users.

Prevention:

• Escape user input before rendering
• Use Content Security Policy (CSP)
• Validate and sanitize all inputs
• Use templating frameworks with automatic escaping

Cross-Site Request Forgery (CSRF)

CSRF attacks trick users into performing actions they didn't intend to perform.

Prevention:

• Use CSRF tokens
• Verify origin headers
• Implement SameSite cookie attributes

Authentication and Authorization

Secure Password Storage

• Never store passwords in plain text
• Use strong hashing algorithms (bcrypt, argon2)
• Implement password complexity requirements
• Consider password managers and 2FA

Session Management

• Use secure, HTTP-only cookies
• Implement session timeouts
• Regenerate session IDs after login
• Validate sessions on every request

OAuth and Third-Party Authentication

When using OAuth:

• Validate tokens properly
• Store tokens securely
• Handle refresh tokens correctly
• Implement proper logout

Data Protection

Encryption

• Use HTTPS for all communications (TLS 1.2+)
• Encrypt sensitive data at rest
• Use secure key management
• Never commit secrets to version control

Input Validation

Validate all inputs:

• Client-side validation (user experience)
• Server-side validation (security requirement)
• Whitelist acceptable values when possible
• Reject suspicious patterns

Security Headers

Implement security headers:

• Content-Security-Policy: Restricts resource loading
• X-Frame-Options: Prevents clickjacking
• X-Content-Type-Options: Prevents MIME type sniffing
• Strict-Transport-Security: Enforces HTTPS

Dependency Management

Keep Dependencies Updated

• Regularly update dependencies
• Subscribe to security advisories
• Use dependency scanning tools
• Review dependency licenses

Security Testing

Incorporate security into your development process:

• Static analysis: Automated code scanning
• Dynamic testing: Runtime vulnerability scanning
• Penetration testing: Manual security reviews
• Code reviews: Peer security assessments

Incident Response

Prepare for security incidents:

• Have an incident response plan
• Implement logging and monitoring
• Define roles and responsibilities
• Practice incident response procedures

Conclusion

Security is an ongoing process that requires vigilance and continuous improvement. By following these practices and staying informed about emerging threats, you can build more secure applications.