SKILL.md
Security Hardening (FIX phase)
Overview
Turn findings into correct, verified fixes. Fix the root cause at the right layer, add defense in depth, then re-test to prove the hole is closed.
Core principle: A fix you didn't re-test is a hope, not a fix. Reproduce the original exploit and confirm it now fails.
Process per finding
- Root cause — why is untrusted data reaching the sink? Fix there, not by blocklisting symptoms.
- Apply the secure pattern — see table below.
- Defense in depth — add a second independent control (validation + parameterization, etc.).
- Re-test — rerun the exact PoC from
active-pentest/the audit; confirm it fails now. - Regression — add a test so it can't silently come back.
Secure-pattern quick reference
| Vulnerability | Root-cause fix | Defense in depth |
|---|---|---|
| SQL/NoSQL injection | Parameterized queries / ORM bindings; allowlist dynamic identifiers | Least-privilege DB user; input validation |
| Command injection | Avoid shell; use exec arrays / safe APIs; no shell interpolation | Allowlist args; drop privileges |
| XSS | Context-aware output encoding; framework auto-escape; textContent |
CSP; sanitize HTML (DOMPurify); HttpOnly cookies |
| Broken access control / IDOR | Enforce authz server-side on every action; scope queries to the user | Deny-by-default; centralized policy checks |
| Mass assignment | Explicit allowlist of bindable fields (DTO/schema) | Separate read/write models |
| Broken auth | bcrypt/argon2; CSPRNG tokens; rotate session on login | MFA; rate limit; short token TTL + revocation |
| Crypto failures | Vetted libs; AES-GCM; TLS everywhere; no homemade crypto | Key management/rotation; HSTS |
| SSRF | Allowlist destinations; resolve+validate; block metadata/internal IPs | Egress firewall; no raw URL fetch |
| Insecure deserialization | Safe formats (JSON); yaml.safe_load; signed payloads |
Type allowlists; isolation |
| Secrets in code | Move to env/secret manager; rotate the exposed secret | Secret scanning in CI; short-lived tokens |
| Security misconfig | Disable debug; least-priv CORS; remove default creds | Hardened baseline; config review in CI |
| Mobile insecure storage | Keychain/Keystore + encryption | Pinning; no secrets in binary |
Validation rules of thumb
- Validate on the server — client validation is UX, not security.
- Allowlist > blocklist — define what's permitted, reject the rest.
- Encode for the sink, not the source — same data needs different encoding per context.
- Fail closed — deny by default; an error should not grant access.
Re-test gate (don't skip)
[ ] Re-ran the original PoC → it now fails / is blocked
[ ] Added an automated regression test
[ ] Checked the fix didn't just move the sink elsewhere
[ ] Verified no similar instances exist (grep the pattern across the codebase)Output
For each finding: root cause · the fix (diff/pattern) · re-test result (PoC now fails) · regression test added. Update the findings register status → Closed.
Common mistakes
- Patching the one reported line while identical sinks remain elsewhere — grep for siblings.
- Blocklist filters (e.g. stripping
<script>) that attackers trivially bypass. - Client-side-only fixes for server-side problems.
- Marking "fixed" without rerunning the exploit.