exposure

name	exposure
description	For one (finding, dependent) pair, decide whether the dependent's published code actually reaches the upstream library finding. Emit one CSAF 2.0 product_status verdict so scrutineer can record affected vs not_affected and stamp the right VEX justification.
license	MIT
allowed-tools	Read,Write,Glob,Grep,WebFetch,LS
metadata	{"scrutineer.version":1,"scrutineer.output_file":"report.json","scrutineer.output_kind":"exposure","scrutineer.requires_remote":true}

exposure

Scrutineer just finished a security-deep-dive on a library and is now walking that library's top dependents. For each dependent, this skill answers the same question reachability asks application-side, but scoped to a single upstream finding: does this dependent's code path the bug requires actually exist?

Your verdict feeds CSAF VEX export, so use the CSAF product_status vocabulary. The four legal status values are known_affected, known_not_affected, under_investigation, fixed. justification is a CSAF VEX flag label and only applies when status is known_not_affected.

Workspace

• ./src — a per-scan copy of the dependent's cloned source
• ./context.json — has scrutineer.api_base, scrutineer.token, scrutineer.finding_id, scrutineer.dependent_id
• ./report.json — write your verdict here
• ./schema.json — output shape

Inputs

Fetch the upstream finding so you know what to look for:

GET {api_base}/findings/{finding_id}
Authorization: Bearer {token}

Read title, location, sinks, trace, boundary and affected. These tell you which call inside the library is dangerous, the input shape it needs, and which versions are vulnerable.

Procedure

1. Find how this dependent uses the library. Grep ./src for imports/requires of the library package (the finding's repository_url / affected field name it). If the lockfile lists the lib but no source file uses the dangerous symbol, status is known_not_affected with justification vulnerable_code_not_in_execute_path.

2. Check the pinned version against affected. If the dependent pins a version outside the affected range, status is known_not_affected with justification vulnerable_code_not_present (the consumer ships the library, but the build it ships does not contain the vulnerable code). component_not_present is reserved for the case where the library itself is not in the dependent at all.

3. Trace from a public entry point to the call. Use the same heuristics reachability uses: request handlers, CLI entry points, library exports. If the only callers are test fixtures or admin-only tooling, status is known_not_affected with justification vulnerable_code_not_in_execute_path.

4. Check the dependent's own validation around the call. A size cap, schema check, or safe-mode flag the dependent applies before forwarding to the library may neutralise the bug. If you can show that, status is known_not_affected with justification inline_mitigations_already_exist.

5. If a real call path exists and reaches the sink with attacker-controlled input, status is known_affected. Leave justification empty.

6. If the upstream finding has a fix_version set and the dependent pins at or above it, status is fixed. Leave justification empty.

7. If the dependent's code base is too large to be confident in two-pass triage, status is under_investigation. Say so in rationale.

Output

Write ./report.json:

{
  "status": "known_not_affected",
  "justification": "vulnerable_code_not_in_execute_path",
  "rationale": "Dependent foo imports bar but only calls bar.SafeParse(). The vulnerable bar.UnsafeParse() is never referenced.",
  "spec_version": 1
}

Keep rationale to one paragraph, citing the file paths you checked. The scrutineer UI displays it under the per-dependent table on the finding page.