#	Vulnerability	What to Check
1	Injection	SQL, NoSQL, LDAP, OS commands—parameterize everything
2	Broken Auth	Session management, credential storage, MFA
3	Sensitive Data	Encryption at rest/transit, PII exposure, logging secrets
4	XXE	XML parsers disabled external entities?
5	Broken Access	IDOR, privilege escalation, missing authZ checks
6	Misconfig	Default credentials, error messages, headers
7	XSS	Input sanitization, output encoding, CSP
8	Insecure Deserialization	Untrusted data → object creation
9	Vulnerable Dependencies	npm audit, Dependabot, known CVEs
10	Logging & Monitoring	Audit trails, alerting, incident detection

Threat Modeling (STRIDE)

Threat	Question	Mitigation
Spoofing	Can attacker impersonate?	Strong authentication
Tampering	Can data be modified?	Integrity checks, signatures
Repudiation	Can actions be denied?	Audit logging
Information Disclosure	Can secrets leak?	Encryption, access control
Denial of Service	Can system be overwhelmed?	Rate limiting, quotas
Elevation of Privilege	Can attacker gain access?	Least privilege, authZ

Code Review Security Lens

Authentication

□ Passwords hashed with bcrypt/argon2 (not MD5/SHA1)
□ No hardcoded credentials
□ Session tokens are random, rotated, and expire
□ Failed login attempts are rate-limited
□ MFA supported where appropriate

Authorization

□ Every endpoint has explicit access control
□ No security through obscurity (hidden URLs)
□ Resource ownership verified before access
□ Admin functions require elevated auth
□ Deny by default, allow explicitly

Input Validation

□ All input validated on server (not just client)
□ Allowlist validation preferred over blocklist
□ File uploads restricted by type and size
□ URL redirects validated against allowlist
□ JSON/XML parsing has size limits

Data Protection

□ Sensitive data encrypted at rest
□ TLS 1.2+ for data in transit
□ API keys/secrets in env vars, not code
□ PII minimized and retention limited
□ Logs don't contain passwords/tokens/PII

Dependencies

□ npm audit / pip audit / cargo audit clean
□ No deprecated or unmaintained packages
□ Dependabot or Renovate enabled
□ Lock files committed
□ Known CVE check before release

Quick Security Questions

Before shipping, ask:

What's the worst thing an attacker could do?
What data could leak if this endpoint is exposed?
Who should NOT have access to this?
What happens if input is malicious?
Are we trusting anything we shouldn't?

Common Vulnerabilities by Language

Language	Watch For
JavaScript	Prototype pollution, eval(), innerHTML
TypeScript	Type assertions bypassing validation
Python	pickle deserialization, format strings
SQL	String concatenation in queries
Shell	Command injection, unquoted variables

Security Headers Checklist

Content-Security-Policy: default-src 'self'
X-Content-Type-Options: nosniff
X-Frame-Options: DENY
Strict-Transport-Security: max-age=31536000
X-XSS-Protection: 0 (deprecated, use CSP)

Incident Response Connection

When vulnerability found:

Assess: What's the blast radius?
Contain: Can we disable the feature?
Fix: Patch the vulnerability
Verify: Confirm fix works
Learn: Update review checklist

Synapses

See synapses.json for connections.

Security Review Skill

Security Review Skill

Core Principle

OWASP Top 10 Checklist