Security audit

Security Audit

A pragmatic, OWASP-flavored review. The goal is finding real risks, not generating a checklist that nobody acts on.

When to use

• "Audit X for security issues"
• "Review this code for vulnerabilities"
• "Is this safe to deploy?"
• "Harden the auth flow"
• "Check for secrets / OWASP issues"

Scope this first

Security is infinite; your time is not. Ask:

• What are you protecting? Data (PII, payments, secrets)? Availability? Integrity?
• Who's the threat model? Anonymous internet, authenticated users, malicious insiders, supply chain?
• What's in scope this round? Whole repo, one module, the auth surface, the public API?

If the user can't answer, suggest starting with the public attack surface (anything reachable without auth) and secret handling.

Procedure

1. Inventory the attack surface — public endpoints, file uploads, deserialization points, command/SQL/template execution, third-party callbacks
2. Walk the checklist below, category by category
3. For each finding: confirm it's exploitable (or be honest that it's theoretical), estimate severity, propose a fix
4. Report by severity (see Output format)

Checklist

Input handling

• Every external input has explicit validation (type, length, range, format)
• User input never built into SQL via string concat → parameterized queries only
• User input never passed to eval, exec, Function(), system(), shell, deserializer
• Path inputs are normalized and checked against a base directory (no ../ traversal)
• Uploaded files: type checked by content, not extension; stored outside web root; size-limited; renamed
• Rendered output is context-correctly escaped (HTML / JS / URL / SQL / shell each need their own escaper)
• No regex with catastrophic backtracking on user input (ReDoS)
• XML/YAML parsers disable external entities and unsafe loaders

AuthN (authentication)

• Passwords hashed with argon2, bcrypt, or scrypt — never MD5/SHA1/SHA256-only
• Login is rate-limited and lockout/back-off is implemented
• Session tokens are long, random, server-side invalidatable
• Cookies: HttpOnly, Secure, SameSite=Lax or Strict
• Password reset tokens are single-use, short-lived, and tied to user + email
• MFA available for sensitive accounts
• Logout actually invalidates the session server-side

AuthZ (authorization)

• Every endpoint checks "is this user allowed to do this to this resource?"
• No relying on hidden fields / client-supplied IDs / referer headers for permissions
• Object-level authorization (IDOR) checked: GET /orders/42 verifies 42 belongs to the caller
• Admin-only actions checked on server, not just hidden in UI
• Multi-tenant boundaries enforced in every query

Secrets

• No secrets in source, history, CI logs, error responses, or client bundles
• Secrets loaded from env / secret manager / vault — not files in the repo
• .env, .pem, key material in .gitignore
• Rotate-able: nothing baked in at build time that can't be changed
• Quick scan: git log -p -S 'BEGIN PRIVATE KEY', grep -RIn 'api[_-]\?key\|secret\|password' .

Transport & headers

• HTTPS enforced (redirect from HTTP, HSTS header)
• CORS configured intentionally (no Access-Control-Allow-Origin: * for credentialed APIs)
• Content-Security-Policy set
• X-Frame-Options or CSP frame-ancestors
• Referrer-Policy: strict-origin-when-cross-origin or stricter

CSRF / SSRF

• State-changing requests require CSRF token or are SameSite + auth-header-based
• Outbound requests to user-supplied URLs are blocked from internal ranges (169.254, 127.0.0.0/8, 10/8, 192.168/16, ::1) and metadata endpoints (169.254.169.254)

Dependencies & supply chain

• Lockfile committed
• Audit tool run cleanly: npm audit, pnpm audit, composer audit, pip-audit, cargo audit, bundle audit
• No abandoned/unmaintained critical deps
• CI/build secrets scoped (no admin-level GitHub tokens in PR builds from forks)
• Pinned third-party CDN scripts use SRI

Logging & errors

• No secrets, passwords, tokens, or PII in logs
• No stack traces leaked to end users in production
• Errors return generic messages externally, full detail internally
• Audit log for sensitive actions (login, role change, payment, deletion)

Data

• PII encrypted at rest where regulation requires
• Backups exist and have been restored at least once
• Deletes are real deletes (or documented soft-delete with retention policy)
• Database access uses least-privilege accounts (the app doesn't connect as DB owner)

Quick scans to run

# Hardcoded secrets (rough)
grep -RInE '(api[_-]?key|secret|password|token)\s*[:=]\s*["'\''][^"'\'']{6,}' \
  --include='*.{js,ts,jsx,tsx,php,py,rb,go,rs,java,kt,yml,yaml,env}' .

# Private key material
grep -RIn 'BEGIN .* PRIVATE KEY' .

# Eval-like primitives
grep -RInE '\b(eval|exec|Function|setTimeout|setInterval)\s*\(' --include='*.{js,ts}' .

# Raw SQL concatenation (heuristic, lots of false positives)
grep -RInE 'SELECT .*\+ .*\bFROM|"\s*\+\s*\$|f"SELECT.*\{' .

# Dependency audit (pick what applies)
npm audit --omit=dev || pnpm audit || composer audit || pip-audit || cargo audit

Treat all greps as leads, not verdicts.

Severity rubric

Tag	Meaning
🔴 Critical	Remote exploit possible by unauthenticated user; data loss; account takeover. Fix before next deploy.
🟠 High	Exploit possible by authenticated user, or critical with significant preconditions. Fix this sprint.
🟡 Medium	Defense-in-depth gap, hardening recommendation, theoretical exploit.
🟢 Low	Best-practice nit, not directly exploitable.
💭 Question	Looks suspicious but you need more context to be sure.

Output format

## Security audit: <scope>

**Threat model assumed:** <e.g. "anonymous internet attacker against public API">
**Scanned:** <files / modules / endpoints>

### 🔴 Critical
- `path/to/file.ts:42` — <finding>. **Exploit:** <how>. **Fix:** <what>.

### 🟠 High
- …

### 🟡 Medium
- …

### 🟢 Low
- …

### 💭 Questions
- …

### ✅ Looked at and clean
- <category> — <one sentence on what you verified>

Anti-patterns

• ❌ "Looks fine 👍" — say what you actually checked
• ❌ Crying wolf — marking every finding "critical" devalues real ones
• ❌ Listing CVEs from npm audit without checking if the vulnerable path is reachable
• ❌ Recommending DOMPurify / helmet / a WAF as the only fix to an injection bug — fix the root cause too
• ❌ Suggesting custom crypto. Don't.

Useful references

• OWASP Top 10
• OWASP ASVS — exhaustive checklist
• OWASP Cheat Sheet Series — practical, per-topic