Skill — Security Review

When this skill activates

Any task involving user identity, data protection, payments, file handling, or credential management. When in doubt: load this skill.

Mandatory actions when this skill is active

Before writing any code

1. Switch to security-reviewer.md persona.
2. Read the existing code in every file you will touch.
3. Identify existing vulnerabilities before introducing new ones.
4. Review SECURITY.md for org-specific policies.

During implementation

Apply these patterns by default — do not wait to be asked:

Authentication

• Passwords: bcrypt (cost ≥ 12) or argon2id. Never MD5, SHA1, or unsalted SHA256.
• Tokens: cryptographically random, minimum 32 bytes. Use crypto.randomBytes(32).
• JWT: short expiry (15 min access, 7 day refresh). Store refresh in httpOnly cookie.
• Sessions: regenerate session ID on privilege escalation. Invalidate on logout.

Authorisation

• Check permissions server-side on every request. Never trust client-sent roles.
• Use deny-by-default. Grant only the minimum required permissions.
• Log every authorisation failure with user ID, resource, and timestamp.

Input handling

• Validate all input at the boundary (route handler). Reject, never sanitise.
• SQL: parameterised queries only. Never string concatenation.
• File uploads: validate MIME type server-side. Never trust Content-Type header alone.
• Redirect URLs: whitelist allowed domains. Never redirect to arbitrary user input.

Secrets

• Environment variables only. Never in source code. Never in git.
• Rotate credentials if there is any suspicion of exposure.
• Use a secrets manager (Vault, AWS Secrets Manager) in production.

After implementation

Run the OWASP checklist from security-reviewer.md against your own diff. Write findings to .planning/phases/phase-N/SECURITY-REVIEW-N.md.

Red lines (stop immediately if you encounter these)

• A hardcoded secret, password, or API key anywhere in the codebase
• A SQL query built by string concatenation
• A password comparison using == instead of a constant-time function
• JWT verification being skipped or using none algorithm
• User input being passed directly to eval(), exec(), or shell commands

Self-check before task completion

Before marking a task done when this skill was active:

• [ ] Did I read the full SKILL.md before starting? (Not just the triggers)
• [ ] Did I activate the corresponding persona file?
• [ ] Did I apply every mandatory action in this skill, not just the ones

I remembered off the top of my head?

• [ ] If this skill produced an output file (review, security report, etc.),

has that file been written to the correct path?

When you find a vulnerability

Do not silently fix it and move on. For every vulnerability found:

1. Stop the current task.
2. Classify it using the severity model (CRITICAL / HIGH / MEDIUM / LOW).
3. For CRITICAL or HIGH: Write to SECURITY-REVIEW-N.md immediately.

Tell the user. Do not proceed with ANY other work until acknowledged.

1. For MEDIUM: Write to SECURITY-REVIEW-N.md. Finish the current task.

Flag at the end of the SUMMARY.md.

1. For LOW: Write to SECURITY-REVIEW-N.md. Note in SUMMARY.md.

The worst security outcome is a vulnerability that was found, noted mentally, and then forgotten when context rolled over. Write it down. Always.