# Staff Security Engineer — Round 2 Review

**Branch:** `colonyos/when_you_output_followups_in_the_thread_on_slack_a938599349`
**PRD:** `cOS_prds/20260331_190640_prd_you_are_a_code_assistant_working_on_behalf_of_the_engineering_team_the_following.md`
**Date:** 2026-03-31

## Checklist

### Completeness
- [x] All functional requirements from the PRD are implemented (FR-1 through FR-5)
- [x] All tasks in the task file are marked complete
- [x] No placeholder or TODO code remains

### Quality
- [x] All 127 tests pass (test_sanitize.py + test_slack_formatting.py)
- [x] Code follows existing project conventions
- [x] No unnecessary dependencies added
- [x] No unrelated changes included

### Safety
- [x] No secrets or credentials in committed code
- [x] No destructive database operations
- [x] Error handling present for failure cases (try/except around cost/duration parsing, fallback chains for review parsing)

## Security Assessment

### Sanitization Pipeline — Correct and Complete

The implementation applies a double-sanitization pattern at all 7 untrusted content ingress points:

1. `sanitize_untrusted_content()` — strips XML-like tags (prevents prompt delimiter injection)
2. `sanitize_for_slack()` — escapes mrkdwn metacharacters, neutralizes mentions and link injection

**Ingress points verified:**
- `_run_sequential_implement()` → task description in phase header (line 875)
- `_format_task_outline_note()` → task descriptions in bullet list
- `_format_task_list_with_descriptions()` → task descriptions with cost/duration
- `_extract_review_findings_summary()` → FINDINGS bullet text (3 fallback paths all sanitized)

### Round 1 Gaps — Now Closed

The two low-severity gaps identified in my Round 1 review have been addressed:

1. **Non-HTTP link schemes**: `_SLACK_LINK_INJECTION_RE` now uses `[a-zA-Z][a-zA-Z0-9+.-]*://` to match any URI scheme (`mailto:`, `slack://`, `ftp://`, etc.). Tests `test_neutralizes_mailto_link_injection` and `test_neutralizes_slack_protocol_link_injection` verify this.

2. **User mention injection**: `_SLACK_MENTION_RE` now covers `<@U12345>`, `<@W12345>`, and `<@B12345>` patterns with optional `|display` text. Tests `test_neutralizes_user_mention_injection`, `test_neutralizes_user_mention_with_display`, and `test_neutralizes_bot_mention` verify this.

### Truncation — Defense in Depth

The `_truncate_slack_message()` function caps all output at 3,000 characters with newline-boundary awareness. This is applied:
- Internally in each formatting function (`_format_task_outline_note`, `_format_implement_result_note`, `_format_review_round_note`)
- Externally at each `slack_note()` call site (belt-and-suspenders)

This double truncation is intentional and correct — the internal truncation is the primary defense, and the call-site truncation is a safety net against future formatting functions that might skip it.

### Information Leakage — Mitigated

Review findings are truncated to 2 per reviewer at 80 chars each, preventing a review that echoes large code blocks or internal paths from leaking excessive architecture detail into Slack channels.

### Remaining Observations (Non-Blocking)

1. **No audit logging for sanitization events**: When `sanitize_for_slack()` neutralizes a mention or link, there's no log entry. `strip_slack_links()` logs at DEBUG level, but `sanitize_for_slack()` does not. This would be useful for detecting injection attempts. Low priority — the existing `strip_slack_links` DEBUG logging sets a pattern to follow later.

2. **`_SLACK_BARE_LINK_RE` only catches http/https**: In `sanitize_for_slack()`, the bare link regex `_SLACK_BARE_LINK_RE` (defined at line 51) only matches `https?://`. A bare `<mailto:user@corp.com>` without display text would not be stripped. However, the XML sanitizer upstream would catch the angle brackets, and bare links without display text are lower-risk (no phishing label). Non-blocking.

## VERDICT: approve

## FINDINGS:
- [src/colonyos/sanitize.py]: Non-HTTP bare link regex (`_SLACK_BARE_LINK_RE`) only catches http/https — bare `<mailto:...>` without display text not covered. Low risk due to upstream XML sanitizer.
- [src/colonyos/sanitize.py]: No audit logging when mentions/links are neutralized. Would aid injection detection but not a security gap.

## SYNTHESIS:
The implementation is secure and production-ready. All injection vectors identified in Round 1 have been closed with targeted regex expansions and corresponding test coverage. The sanitization architecture — `sanitize_untrusted_content()` then `sanitize_for_slack()` applied at each content ingress point — is the correct pattern: sanitize inputs, not outputs. The 3,000-char truncation applied both internally and at call sites provides defense-in-depth against information leakage. The two remaining observations are low-priority hardening opportunities that do not block shipping.
