# Review by Staff Security Engineer (Round 3)

## Review Complete

Here's my assessment as **Staff Security Engineer**:

VERDICT: **approve**

### Key Findings

1. **[src/colonyos/instructions/thread_fix.md]** — User-supplied content (`original_prompt`, `fix_request`) is injected into the *system* prompt via template formatting. Sanitization is applied, but defense-in-depth favors keeping untrusted content strictly in the user prompt. **Low severity.**

2. **[src/colonyos/sanitize.py]** — Stripped Slack URLs are silently discarded without logging. For forensic analysis after a security incident, the original URLs would be valuable. **Informational.**

3. **[src/colonyos/orchestrator.py]** — Branch restoration failure in `run_thread_fix()` finally block only logs a warning. Could leave repo on wrong branch for next queue item in watch mode. **Low severity.**

4. **[PRD open question]** — `prd_sha256`/`task_sha256` artifact integrity checks not implemented. Acknowledged as fast-follow. This is the most significant residual risk — an adversary with repo write access could modify planning artifacts between the original run and a fix request.

### What's Done Well

- **Sanitization pipeline** correctly applied to all thread-fix inputs (FR-18–21)
- **`strip_slack_links()`** closes the Slack `<URL|display_text>` attack vector
- **Git ref validation** uses strict allowlist (`[a-zA-Z0-9._/-]`), rejects `..`, shell metacharacters, backticks
- **HEAD SHA verification** prevents force-push TOCTOU attacks
- **Triage agent** runs with `allowed_tools=[]` — zero tool access minimizes prompt injection blast radius
- **Defense-in-depth** — branch name re-validated at point of use in `run_thread_fix()`
- **Thread safety** — `state_lock` protects `fix_rounds` increment and queue mutations
- All **456 tests pass**, including security-specific tests for path traversal, shell injection, and SHA mismatch

The review artifact has been written to `cOS_reviews/reviews/staff-security-engineer/round_3_thread_fix.md`.