Security Review

Overview

Systematically review code for security vulnerabilities, apply secure coding patterns, and ensure applications follow defense-in-depth principles. This skill covers the OWASP Top 10, authentication pattern selection, input validation, secrets management, dependency auditing, security headers, and threat modeling.

Announce at start: "I'm using the security-review skill to assess security posture."

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Phase 1: Scope and Threat Assessment

Goal: Identify the attack surface and prioritize review areas.

Actions

1. Identify all user-facing endpoints and input surfaces
2. Map authentication and authorization boundaries
3. List external dependencies and their trust levels
4. Identify sensitive data flows (PII, credentials, payment)
5. Determine compliance requirements (SOC 2, GDPR, HIPAA)

STOP — Do NOT proceed to Phase 2 until:

• Attack surface is mapped
• Sensitive data flows are identified
• Compliance requirements are known

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Phase 2: OWASP Top 10 Audit

Goal: Systematically check against each OWASP category.

OWASP Top 10 Checklist (2021)

#	Category	Key Check	Pass/Fail
1	Broken Access Control	Authorization verified on every endpoint, deny by default
2	Cryptographic Failures	No plaintext secrets, strong algorithms (AES-256, bcrypt)
3	Injection	Parameterized queries, no string concatenation for SQL/commands
4	Insecure Design	Threat model exists, rate limiting, abuse cases considered
5	Security Misconfiguration	No defaults in production, minimal permissions, error messages leak nothing
6	Vulnerable Components	Dependencies audited, no known CVEs, update policy in place
7	Auth Failures	MFA available, passwords hashed, session management secure
8	Data Integrity Failures	Verify signatures, validate CI/CD pipeline integrity
9	Logging Failures	Log auth events, access control failures, input validation failures
10	SSRF	Validate/allowlist URLs, no internal network access from user input

STOP — Do NOT proceed to Phase 3 until:

• All 10 categories are checked
• Findings are documented with severity

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Phase 3: Deep Review by Category

Goal: Apply detailed security patterns to identified issues.

Auth Pattern Selection Table

Pattern	Use When	Key Requirements
JWT	Stateless APIs, microservices, mobile backends	RS256 for multi-service; access token 15min max; HttpOnly cookies
Session-based	Traditional web apps, server-rendered pages	Server-side storage; HttpOnly + Secure + SameSite cookies; CSRF tokens
OAuth2/OIDC	Third-party login, SSO, delegated auth	Authorization Code + PKCE; validate ID token claims; server-side token storage
Passkeys/WebAuthn	Passwordless, high-security apps	Phishing-resistant; store public keys only; support multiple per account

JWT Security Checklist

Aspect	Guidance
Signing	RS256 (asymmetric) for multi-service, HS256 for single service
Expiry	Access token: 15 minutes max. Refresh token: 7 days max
Storage	HttpOnly cookie (web) or secure storage (mobile). Never localStorage
Refresh	Rotate refresh tokens on use, invalidate on logout
Payload	Minimal claims (sub, exp, iat, roles). No sensitive data

Input Validation Patterns

Allow-List Validation (always prefer over block-list):

# Good: allow-list
ALLOWED_SORT_FIELDS = {'name', 'created_at', 'price'}
if sort_field not in ALLOWED_SORT_FIELDS:
    raise ValidationError("Invalid sort field")

# Bad: block-list (always incomplete)
BLOCKED_CHARS = ['<', '>', '"']

Parameterized Queries (never concatenate user input):

# Good: parameterized
cursor.execute("SELECT * FROM users WHERE id = %s", (user_id,))

# Bad: SQL injection vulnerability
cursor.execute(f"SELECT * FROM users WHERE id = {user_id}")

File Upload Validation

• Validate MIME type server-side (not just extension)
• Enforce file size limits
• Generate random filenames (never use user-supplied names)
• Store uploads outside the web root
• Scan for malware if accepting from untrusted users

STOP — Do NOT proceed to Phase 4 until:

• All identified issues have remediation recommendations
• Auth patterns are correctly applied
• Input validation is comprehensive

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Phase 4: Infrastructure and Dependency Hardening

Goal: Secure the deployment environment and supply chain.

Secrets Management Rules

Environment	Method
Development	.env files (git-ignored)
CI/CD	Pipeline secrets (GitHub Secrets, GitLab CI vars)
Production	Secrets manager (AWS Secrets Manager, Vault, GCP Secret Manager)

Secrets Never List

• Never hard-code secrets in source code
• Never commit .env files to git
• Never log secrets (even at debug level)
• Never pass secrets as command-line arguments
• Never use the same secrets across environments

Dependency Auditing Commands

# Node.js
npm audit
npx socket-security audit

# Python
pip-audit
safety check

# Go
govulncheck ./...

# Rust
cargo audit

Security Headers

Header	Value	Purpose
Content-Security-Policy	default-src 'self' (customize per app)	Prevents XSS, data injection
Strict-Transport-Security	max-age=63072000; includeSubDomains	Forces HTTPS
X-Content-Type-Options	nosniff	Prevents MIME sniffing
X-Frame-Options	DENY or SAMEORIGIN	Prevents clickjacking
Referrer-Policy	strict-origin-when-cross-origin	Controls referer leakage
Permissions-Policy	Disable unused APIs	Limits browser feature access

CORS Rules

• Never use Access-Control-Allow-Origin: * with credentials
• Allowlist specific origins
• Restrict allowed methods and headers to what is needed

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Phase 5: Threat Modeling (STRIDE)

Goal: For new features or significant changes, walk through each threat category.

Threat	Question	Mitigation
Spoofing	Can an attacker pretend to be someone else?	Strong authentication, MFA
Tampering	Can data be modified without detection?	Integrity checks, signatures
Repudiation	Can a user deny performing an action?	Audit logging
Information Disclosure	Can sensitive data leak through errors, logs, or side channels?	Error sanitization, encryption
Denial of Service	Can the system be overwhelmed?	Rate limits, resource quotas
Elevation of Privilege	Can a user gain permissions they should not have?	Least privilege, RBAC

For each identified threat:

1. Document the threat and attack vector
2. Assess likelihood and impact
3. Define mitigations
4. Verify mitigations are implemented and tested

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Decision Table: Security Review Depth

Change Type	Review Depth	Focus Areas
Auth/session changes	Full STRIDE + OWASP	All categories
User input handling	Injection + validation focus	OWASP 1, 3, 10
Dependency update	CVE scan + changelog review	OWASP 6
API endpoint addition	Access control + input validation	OWASP 1, 3, 5
Config/infrastructure	Secrets + headers + misconfig	OWASP 2, 5
File upload feature	Injection + SSRF + malware	OWASP 3, 10

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Anti-Patterns / Common Mistakes

Anti-Pattern	Why It Is Wrong	Correct Approach
Client-side only validation	Easily bypassed	Always validate server-side
Storing tokens in localStorage	XSS can steal them	Use HttpOnly cookies
Block-list input validation	Always incomplete	Use allow-list validation
Generic error messages in production	May leak internal details	Sanitize errors, log details server-side
Same secrets across environments	Breach of one compromises all	Unique secrets per environment
Ignoring dependency CVEs	Known vulnerabilities are actively exploited	Audit and update regularly
CORS wildcard with credentials	Defeats CORS protection entirely	Allowlist specific origins
Logging sensitive data	Log exposure creates data breach	Never log secrets, PII, or tokens

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Secrets Rotation Schedule

Secret Type	Rotation Frequency	After Suspected Compromise
API keys	Every 90 days	Immediately
Database passwords	Every 90 days	Immediately
Encryption keys	Annually (support key versioning)	Immediately
JWT signing keys	Every 6 months	Immediately
OAuth client secrets	Every 90 days	Immediately

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Subagent Dispatch Opportunities

Task Pattern	Dispatch To	When
Scanning different OWASP categories in parallel	Agent tool with subagent_type="Explore" (one per category)	When reviewing a large codebase across multiple vulnerability types
Authentication flow analysis	Agent tool with subagent_type="general-purpose"	When auth implementation spans multiple files/services
Dependency vulnerability scanning	Bash tool with run_in_background=true	When running npm audit or similar tools concurrently

Follow the dispatching-parallel-agents skill protocol when dispatching.

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Integration Points

Skill	Relationship
code-review	Security findings are Critical category issues
senior-backend	Backend hardening follows security review findings
senior-fullstack	Auth implementation follows security patterns
acceptance-testing	Security requirements become acceptance criteria
performance-optimization	Rate limiting serves both security and performance
systematic-debugging	Security incidents trigger debugging workflow

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Skill Type

FLEXIBLE — Adapt the depth of review to the change type using the decision table. The OWASP checklist and STRIDE analysis are strongly recommended for any auth or input-handling changes. Secrets management rules are non-negotiable.