# Phase 12: False Positive Filtering + Active Verification

Before producing findings, run every candidate through this filter.

**Two modes:**

**Daily mode (default, `/mk:cso`):** 8/10 confidence gate. Zero noise. Only report what you're sure about.
- 9-10: Certain exploit path. Could write a PoC.
- 8: Clear vulnerability pattern with known exploitation methods. Minimum bar.
- Below 8: Do not report.

**Comprehensive mode (`/cso --comprehensive`):** 2/10 confidence gate. Filter true noise only (test fixtures, documentation, placeholders) but include anything that MIGHT be a real issue. Flag these as `TENTATIVE` to distinguish from confirmed findings.

**Hard exclusions — automatically discard findings matching these:**

1. Denial of Service (DOS), resource exhaustion, or rate limiting issues — **EXCEPTION:** LLM cost/spend amplification findings from Phase 7 (unbounded LLM calls, missing cost caps) are NOT DoS — they are financial risk and must NOT be auto-discarded under this rule.
2. Secrets or credentials stored on disk if otherwise secured (encrypted, permissioned)
3. Memory consumption, CPU exhaustion, or file descriptor leaks
4. Input validation concerns on non-security-critical fields without proven impact
5. GitHub Action workflow issues unless clearly triggerable via untrusted input — **EXCEPTION:** Never auto-discard CI/CD pipeline findings from Phase 4 (unpinned actions, `pull_request_target`, script injection, secrets exposure) when `--infra` is active or when Phase 4 produced findings. Phase 4 exists specifically to surface these.
6. Missing hardening measures — flag concrete vulnerabilities, not absent best practices. **EXCEPTION:** Unpinned third-party actions and missing CODEOWNERS on workflow files ARE concrete risks, not merely "missing hardening" — do not discard Phase 4 findings under this rule.
7. Race conditions or timing attacks unless concretely exploitable with a specific path
8. Vulnerabilities in outdated third-party libraries (handled by Phase 3, not individual findings)
9. Memory safety issues in memory-safe languages (Rust, Go, Java, C#)
10. Files that are only unit tests or test fixtures AND not imported by non-test code
11. Log spoofing — outputting unsanitized input to logs is not a vulnerability
12. SSRF where attacker only controls the path, not the host or protocol
13. User content in the user-message position of an AI conversation (NOT prompt injection)
14. Regex complexity in code that does not process untrusted input (ReDoS on user strings IS real)
15. Security concerns in documentation files (*.md) — **EXCEPTION:** SKILL.md files are NOT documentation. They are executable prompt code (skill definitions) that control AI agent behavior. Findings from Phase 8 (Skill Supply Chain) in SKILL.md files must NEVER be excluded under this rule.
16. Missing audit logs — absence of logging is not a vulnerability
17. Insecure randomness in non-security contexts (e.g., UI element IDs)
18. Git history secrets committed AND removed in the same initial-setup PR
19. Dependency CVEs with CVSS < 4.0 and no known exploit
20. Docker issues in files named `Dockerfile.dev` or `Dockerfile.local` unless referenced in prod deploy configs
21. CI/CD findings on archived or disabled workflows
22. Skill files that are part of the trusted kit (trusted source)

**Precedents:**

1. Logging secrets in plaintext IS a vulnerability. Logging URLs is safe.
2. UUIDs are unguessable — don't flag missing UUID validation.
3. Environment variables and CLI flags are trusted input.
4. React and Angular are XSS-safe by default. Only flag escape hatches.
5. Client-side JS/TS does not need auth — that's the server's job.
6. Shell script command injection needs a concrete untrusted input path.
7. Subtle web vulnerabilities only if extremely high confidence with concrete exploit.
8. iPython notebooks — only flag if untrusted input can trigger the vulnerability.
9. Logging non-PII data is not a vulnerability.
10. Lockfile not tracked by git IS a finding for app repos, NOT for library repos.
11. `pull_request_target` without PR ref checkout is safe.
12. Containers running as root in `docker-compose.yml` for local dev are NOT findings; in production Dockerfiles/K8s ARE findings.

**Active Verification:**

For each finding that survives the confidence gate, attempt to PROVE it where safe:

1. **Secrets:** Check if the pattern is a real key format (correct length, valid prefix). DO NOT test against live APIs.
2. **Webhooks:** Trace handler code to verify whether signature verification exists anywhere in the middleware chain. Do NOT make HTTP requests.
3. **SSRF:** Trace the code path to check if URL construction from user input can reach an internal service. Do NOT make requests.
4. **CI/CD:** Parse workflow YAML to confirm whether `pull_request_target` actually checks out PR code.
5. **Dependencies:** Check if the vulnerable function is directly imported/called. If it IS called, mark VERIFIED. If NOT directly called, mark UNVERIFIED with note: "Vulnerable function not directly called — may still be reachable via framework internals, transitive execution, or config-driven paths. Manual verification recommended."
6. **LLM Security:** Trace data flow to confirm user input actually reaches system prompt construction.

Mark each finding as:
- `VERIFIED` — actively confirmed via code tracing or safe testing
- `UNVERIFIED` — pattern match only, couldn't confirm
- `TENTATIVE` — comprehensive mode finding below 8/10 confidence

**Variant Analysis:**

When a finding is VERIFIED, search the entire codebase for the same vulnerability pattern. One confirmed SSRF means there may be 5 more. For each verified finding:
1. Extract the core vulnerability pattern
2. Use the Grep tool to search for the same pattern across all relevant files
3. Report variants as separate findings linked to the original: "Variant of Finding #N"

**Parallel Finding Verification:**

For each candidate finding, launch an independent verification sub-task using the Agent tool. The verifier has fresh context and cannot see the initial scan's reasoning — only the finding itself and the FP filtering rules.

Prompt each verifier with:
- The file path and line number ONLY (avoid anchoring)
- The full FP filtering rules
- "Read the code at this location. Assess independently: is there a security vulnerability here? Score 1-10. Below 8 = explain why it's not real."

Launch all verifiers in parallel. Discard findings where the verifier scores below 8 (daily mode) or below 2 (comprehensive mode).

If the Agent tool is unavailable, self-verify by re-reading code with a skeptic's eye. Note: "Self-verified — independent sub-task unavailable."
