Conciseness

The 28-line body is lean and assumes Claude's competence — it never explains what vulnerabilities or scanners are, and every line adds non-obvious domain judgment (e.g., "missing Domain can be safer", "express-session httpOnly" defaults). Matches the anchor for content where every token earns its place.

Actionability

The guidance is mostly executable: a concrete procedure ("Start from the changed source path... Trace backward to the user-controlled input and forward to the operation it can influence") and a concrete output spec ("Name the source, sink or sensitive operation, and code path"; "State the smallest regression test or scan evidence"). It falls short of fully executable anchor 5 because there is no worked example contrasting a suppression-only fix with a real one.

Workflow Clarity

The flow is coherent and well-sequenced — trace the dataflow, compare the claimed evidence, apply the Threshold decision gate (with explicit report and do-not-report conditions), then report — but the sequence is implicit in section order rather than an explicit ordered checklist. This matches anchor 4: clear sequence with most checkpoints present, minor gaps.

Progressive Disclosure

The skill is under 50 lines with no external references needed, and its four sections (Scope, Method, Threshold, Reporting) are clearly labeled and well-organized; the simple-skill exception for progressive disclosure applies.

Specificity

The description lists several concrete review criteria — "address the validated root cause", "hiding evidence", "removing intended demo behavior", "weakening regression coverage" — which goes beyond naming the domain. It stops short of anchor 5 because it omits the skill's exclusion scope (dependency/lockfile findings) and the target application context, leaving minor gaps in coverage.

Completeness

Both parts are present: a clear "what" (reviewing vulnerability fixes for root-cause correctness) and a "when" clause ("Use as one lens in a code review run"), so the missing-trigger cap of 3 does not apply. It is not 5 because the when-clause lacks concrete user-facing trigger phrases (e.g., "when reviewing a security fix or remediation PR").

Trigger Term Quality

Natural terms a user would say are present ("vulnerability fixes", "root cause", "regression coverage", "code review"), giving good keyword coverage. Not 5 because common synonyms and variations such as "remediation", "security patch", or "fix verification" are missing.

Distinctiveness Conflict Risk

The niche — verifying that vulnerability *fixes* are correct rather than finding vulnerabilities — is clearly distinct from generic security-review skills, and "one lens in a code review run" positions it. Minor overlap risk with a general security-review skill keeps it below 5.