Security Review Checklist

Apply these security checks when reviewing or writing code that handles sensitive operations.

Authentication

• Authentication required for sensitive endpoints
• Strong password requirements enforced
• Passwords hashed with secure algorithm (bcrypt, argon2)
• Session tokens are cryptographically random
• Session expiration implemented
• Logout invalidates session properly

Authorization

• Authorization checked before data access
• Role-based or attribute-based access control
• Principle of least privilege applied
• Ownership verified before operations
• Admin functions properly protected

Input Validation

• All user input validated
• Input length limits enforced
• Input type/format validated
• Whitelist validation preferred over blacklist
• Validation on server-side (not just client)

Injection Prevention

SQL Injection

• Parameterized queries / prepared statements
• ORM used correctly
• No string concatenation in queries

XSS (Cross-Site Scripting)

• Output encoding/escaping
• Content Security Policy headers
• No innerHTML with user data

Command Injection

• No shell commands with user input
• If unavoidable, strict whitelisting

Data Protection

• Sensitive data encrypted at rest
• Sensitive data encrypted in transit (TLS)
• PII handled according to regulations
• Data minimization (collect only needed data)
• Secure deletion when required

Secrets Management

• No hardcoded credentials
• No secrets in source code
• Secrets in environment variables or vault
• API keys rotatable
• Different secrets per environment

Logging & Monitoring

• Security events logged
• No sensitive data in logs
• Failed authentication attempts logged
• Logs tamper-resistant
• Alerting on suspicious activity

API Security

• Rate limiting implemented
• CORS configured correctly
• API versioning in place
• Proper HTTP methods used
• Sensitive operations use POST/PUT/DELETE

Common Vulnerabilities (OWASP Top 10)

1. Broken Access Control - Verify authorization
2. Cryptographic Failures - Use strong encryption
3. Injection - Parameterize all queries
4. Insecure Design - Threat model considered
5. Security Misconfiguration - Secure defaults
6. Vulnerable Components - Dependencies updated
7. Authentication Failures - Strong auth
8. Data Integrity Failures - Verify signatures
9. Logging Failures - Audit trail present
10. SSRF - Validate URLs, restrict access

Security Red Flags

Look for these patterns that often indicate security issues:

# Dangerous patterns
eval(user_input)           # Code injection
exec(user_input)           # Code injection
os.system(user_input)      # Command injection
f"SELECT * FROM {table}"   # SQL injection
innerHTML = userData       # XSS
password = "hardcoded"     # Hardcoded secret
verify=False               # SSL verification disabled

Secure Alternatives

Insecure	Secure Alternative
MD5/SHA1 for passwords	bcrypt/argon2
pickle.loads(user_data)	JSON with validation
eval()	Explicit parsing
String concatenation SQL	Parameterized queries
Storing plaintext secrets	Environment variables