Application Security Checklist

1. Authentication & Authorization

Enforce strong password policies
Implement multi-factor authentication (MFA)
Ensure proper session management
Verify user roles and permissions
Account lockout after repeated failed logins

2. Input Validation & Data Handling

Validate input on client and server side
Sanitize input to prevent SQL Injection, XSS, command injection
Use parameterized queries / prepared statements
Encode output properly (HTML, JSON, XML)
Restrict file uploads by type, size, and content

3. Data Protection & Encryption

Encrypt sensitive data at rest
Encrypt data in transit using TLS 1.2+
Securely store and hash passwords (bcrypt, Argon2)
Avoid storing sensitive data in logs or URLs
Use secure key management practices

4. Application Configuration

Disable debug or verbose error messages in production
Remove default credentials and unnecessary services
Keep software and dependencies up-to-date
Implement Content Security Policy (CSP) headers
Set proper HTTP headers (X-Frame-Options, X-XSS-Protection, HSTS)

5. Logging & Monitoring

Log security-relevant events
Protect log integrity and restrict access
Monitor for suspicious activity
Set up alerting for critical incidents

6. Error & Exception Handling

Do not expose stack traces or system info
Provide generic error messages to users
Log detailed errors securely for developers

7. API Security

Authenticate all API endpoints
Use tokens or OAuth2 for authorization
Rate-limit API requests
Validate and sanitize all API inputs
Use HTTPS for API communication

8. Third-Party Libraries & Dependencies

Scan for known vulnerabilities in libraries
Use trusted sources for dependencies only
Remove unused or deprecated libraries

9. Secure Development Practices

Follow the principle of least privilege
Conduct regular security code reviews
Perform threat modeling during design phase
Implement secure coding guidelines (OWASP Top 10)
Conduct static and dynamic code analysis

10. Testing & Vulnerability Management

Perform penetration testing periodically
Test for OWASP Top 10 vulnerabilities
Fix vulnerabilities based on severity and priority
Track vulnerability remediation
Implement bug bounty / responsible disclosure programs

11. Backup & Disaster Recovery

Encrypt backups and store securely
Test backup restoration regularly
Maintain incident response plan