Security Checklist

Security Checklist

Quick reference for web application security. Use alongside the security-and-hardening skill.

Table of Contents

• Pre-Commit Checks
• Authentication
• Authorization
• Input Validation
• Security Headers
• CORS Configuration
• Data Protection
• Dependency Security
• Error Handling
• OWASP Top 10 Quick Reference

Pre-Commit Checks

• No secrets in code (git diff --cached | grep -i "password\|secret\|api_key\|token")
• .gitignore covers: .env, .env.local, *.pem, *.key
• .env.example uses placeholder values (not real secrets)

Authentication

• Passwords hashed with bcrypt (≥12 rounds), scrypt, or argon2
• Session cookies: httpOnly, secure, sameSite: 'lax'
• Session expiration configured (reasonable max-age)
• Rate limiting on login endpoint (≤10 attempts per 15 minutes)
• Password reset tokens: time-limited (≤1 hour), single-use
• Account lockout after repeated failures (optional, with notification)
• MFA supported for sensitive operations (optional but recommended)

Authorization

• Every protected endpoint checks authentication
• Every resource access checks ownership/role (prevents IDOR)
• Admin endpoints require admin role verification
• API keys scoped to minimum necessary permissions
• JWT tokens validated (signature, expiration, issuer)

Input Validation

• All user input validated at system boundaries (API routes, form handlers)
• Validation uses allowlists (not denylists)
• String lengths constrained (min/max)
• Numeric ranges validated
• Email, URL, and date formats validated with proper libraries
• File uploads: type restricted, size limited, content verified
• SQL queries parameterized (no string concatenation)
• HTML output encoded (use framework auto-escaping)
• URLs validated before redirect (prevent open redirect)

Security Headers

Content-Security-Policy: default-src 'self'; script-src 'self'
Strict-Transport-Security: max-age=31536000; includeSubDomains
X-Content-Type-Options: nosniff
X-Frame-Options: DENY
X-XSS-Protection: 0  (disabled, rely on CSP)
Referrer-Policy: strict-origin-when-cross-origin
Permissions-Policy: camera=(), microphone=(), geolocation=()

CORS Configuration

// Restrictive (recommended)
cors({
  origin: ['https://yourdomain.com', 'https://app.yourdomain.com'],
  credentials: true,
  methods: ['GET', 'POST', 'PUT', 'PATCH', 'DELETE'],
  allowedHeaders: ['Content-Type', 'Authorization'],
})

// NEVER use in production:
cors({ origin: '*' })  // Allows any origin

Data Protection

• Sensitive fields excluded from API responses (passwordHash, resetToken, etc.)
• Sensitive data not logged (passwords, tokens, full CC numbers)
• PII encrypted at rest (if required by regulation)
• HTTPS for all external communication
• Database backups encrypted

Dependency Security

# Audit dependencies
npm audit

# Fix automatically where possible
npm audit fix

# Check for critical vulnerabilities
npm audit --audit-level=critical

# Keep dependencies updated
npx npm-check-updates

Error Handling

// Production: generic error, no internals
res.status(500).json({
  error: { code: 'INTERNAL_ERROR', message: 'Something went wrong' }
});

// NEVER in production:
res.status(500).json({
  error: err.message,
  stack: err.stack,         // Exposes internals
  query: err.sql,           // Exposes database details
});

OWASP Top 10 Quick Reference

#	Vulnerability	Prevention
1	Broken Access Control	Auth checks on every endpoint, ownership verification
2	Cryptographic Failures	HTTPS, strong hashing, no secrets in code
3	Injection	Parameterized queries, input validation
4	Insecure Design	Threat modeling, spec-driven development
5	Security Misconfiguration	Security headers, minimal permissions, audit deps
6	Vulnerable Components	npm audit, keep deps updated, minimal deps
7	Auth Failures	Strong passwords, rate limiting, session management
8	Data Integrity Failures	Verify updates/dependencies, signed artifacts
9	Logging Failures	Log security events, don't log secrets
10	SSRF	Validate/allowlist URLs, restrict outbound requests

---

Imported from https://github.com/addyosmani/agent-skills by addyosmani. Licensed under MIT. Source: https://github.com/addyosmani/agent-skills/blob/main/references/security-checklist.md