fix-security-vulnerabilities-with-strix — Claude Code skill

---
name: fix-security-vulnerabilities-with-strix
description: Fix security vulnerabilities found by a Strix pentest (open-source CLI or app.strix.ai cloud) — triage by severity, patch the root cause rather than the symptom, and re-run Strix to prove each fix actually closes the exploit. Handles injection, XSS, SSRF, broken access control, IDOR, and other validated findings. Use after a Strix scan reports findings, or when the user asks to remediate, patch, or fix security issues from a strix_runs report, vulnerabilities.json, findings.sarif, or a cloud scan.
license: Apache-2.0
metadata:
  author: usestrix
  homepage: https://docs.strix.ai
---

# Fix Strix findings and verify

Turn validated Strix findings into minimal, correct fixes — and prove they work by re-scanning.

## 1. Triage

Get the findings from wherever the scan ran:

- **OSS CLI** — artifacts in `strix_runs/<run-name>/`:
  - `vulnerabilities/*.md` — one finding per file: description, severity, PoC steps or script, affected code locations, remediation guidance.
  - `vulnerabilities.json` — the same findings as JSON (ids, severity, CWE/CVE, `code_locations` with `fix_before`/`fix_after` suggestions when available).
- **Cloud (app.strix.ai)** — pull findings with the CLI: `strix cloud vulns list --scan-id <scan-id> --json` (or `strix cloud scans get <scan-id> --json | jq '.vulnerabilities'`, or `strix cloud vulns list --severity critical` org-wide). Each finding carries `severity, cwe, endpoint, method, impact, technical_analysis, poc_description, poc_script_code` and, for code findings, `code_file`/`code_diff`/`code_before`/`code_after`. After a fix is verified, mark it with `strix cloud vulns update <id> --status fixed`. See the **managed-pentesting-with-strix** skill for `strix cloud login` and scopes.

Order work by severity: critical → high → medium → low. Every Strix finding was validated with a working proof-of-concept, so do not dismiss findings as false positives without re-testing the PoC yourself.

## 2. Fix

For each finding:

1. Reproduce it with the PoC from the finding file when feasible.
2. Fix the root cause, not the specific payload (parameterize every query instead of blocking one string, and enforce authorization in the handler instead of hiding the endpoint).
3. Prefer the framework's built-in defense (ORM parameterization, template auto-escaping, CSRF middleware, centralized authz) over ad-hoc sanitization.
4. Keep the diff minimal and apply the repo's existing patterns. Finding files often include `fix_before`/`fix_after` snippets — use them as a starting point, not verbatim.

Common finding classes and expected fixes: injection → parameterization/escaping at the sink; IDOR/broken access control → object-level authorization checks; SSRF → allowlist + block internal ranges; XSS → context-aware output encoding + CSP; secrets exposure → rotate the secret AND remove it from code/history; auth issues → fix the server-side check (never client-side).

## 3. Verify by re-running Strix

After fixing, re-scan scoped to the fixed area and confirm the finding is gone. Verify in whichever environment you scanned (or both):

**OSS CLI:**
```bash
# Re-test just the changed files (fast). Resolve the repo's real default
# branch instead of assuming origin/main (many repos use master/develop).
# Avoid the current branch's own upstream as the base — its merge base with
# HEAD would be HEAD, giving an empty diff and a falsely clean result.
DIFF_BASE=$(git symbolic-ref --quiet --short refs/remotes/origin/HEAD 2>/dev/null)
# origin/HEAD can be a dangling symbolic ref — keep it only if its target exists.
git rev-parse --verify --quiet "$DIFF_BASE" >/dev/null 2>&1 || DIFF_BASE=""
if [ -z "$DIFF_BASE" ]; then
  for b in origin/main origin/master origin/develop; do
    git rev-parse --verify --quiet "$b" >/dev/null && DIFF_BASE="$b" && break
  done
fi
# No silent fallback: a guess like HEAD~1 would cover only the last commit of a
# multi-commit fix branch. If no base resolves, ask the user for the base branch
# (or use the focused --instruction verification below, which needs no diff base).
[ -n "$DIFF_BASE" ] || { echo "Set DIFF_BASE to the branch your fix will merge into." >&2; exit 1; }
strix -n -t ./ --scan-mode quick --scope-mode diff --diff-base "$DIFF_BASE" --max-budget 5

# Or re-test with the original finding as focus (no diff base needed)
strix -n -t ./ --instruction "Verify the SQL injection in app/api/search.py is fixed. Original PoC: <poc>" --max-budget 5
```
Exit codes: `2` = findings remain (read the new `strix_runs/<run>/vulnerabilities/` and iterate); `0` = clean **for what was analyzed**. Before trusting a `0`, confirm the run wasn't cut short — check `run.json` for a completed status and compare its `llm_usage.cost` with `--max-budget`: a hard budget stop leaves `status: "stopped"`, but a run that wrapped up on a budget warning records `"completed"` with partial coverage. Give verification enough budget to finish, and prefer re-running the specific PoC as the ground-truth signal.

**Cloud:** rerun with the same config and re-poll, then confirm the finding no longer appears:
```bash
new_id=$(curl -sS "$BASE/scans/$scan_id/rerun" "${auth[@]}" -X POST | jq -r .scan_id)
# poll GET /scans/$new_id until completed, then check its vulnerabilities[]
```
Or, if the cloud scan came from a repo/PR, trigger a fresh PR review on the fix branch (`POST /pr-reviews/start`). The platform also retests a single finding directly: `POST /api/v1/vulnerabilities/{vulnerabilityId}/retest`.

- Also re-run the PoC manually when it is a simple request/script — fastest signal.
- Run the project's own test suite to make sure the fix does not break behavior.

## 4. Report

Summarize per finding: severity, root cause, fix applied (file:line), verification result (re-scan clean / PoC no longer reproduces). Never include live secrets in the report; if a secret leaked, state that rotation is required.