Conciseness

The body is lean and assumes Claude's competence — the intro states the mechanism (named elements resolve as window/document properties) and then goes straight to payloads, targets, detection, and defense with no padding. Minor trims exist (the 'Known exemplars' section and the severity table are marginal), keeping it at the efficient 4-anchor rather than the every-token-earns-its-place 5-anchor.

Actionability

The HTML payloads (single-element clobber, form/input chaining, nonce theft) and the detection console snippet are copy-paste ready, and the defender section gives concrete DOMPurify config and Object.defineProperty fixes. The PoC section stays at the guidance level ('find an HTML-injection sink... confirm via observed network request') without concrete commands, which is the minor gap that keeps it below 5.

Workflow Clarity

The numbered sections (targets → payload patterns → where to inject → detection → PoC → severity → defender) give a clear implicit sequence, and the PoC section includes a verification checkpoint ('Confirm via observed network request to //evil.com (DNS-level via interactsh)'). It falls short of 5 because there is no explicit ordered procedure with error-recovery loops — the flow must be assembled from the sections — but checkpoints are present, so it is above the implicit-checkpoint 3-anchor.

Progressive Disclosure

The single SKILL.md file (~110 lines) is well organized into eight clear sections with no bundle files to disclose, and everything is appropriately self-contained at this size. The cross-references section points to paths outside this bundle (one explicitly marked '(when added)' for a nonexistent file), which is a minor organization/navigation gap rather than the clean one-level-deep reference structure of the 5-anchor.

Specificity

The description names the domain and three concrete actions — 'abuse named HTML elements to overwrite JavaScript global variables', 'bypass CSP', 'hijack object property lookups' — with only minor coverage gaps (no mention of detection or defense, which the body covers). It is not the comprehensive 5-anchor, which would enumerate the full capability set.

Completeness

The 'what' is clearly and explicitly stated (clobbering globals via named HTML elements to bypass CSP and hijack property lookups), but there is no 'Use when...' clause or equivalent explicit trigger guidance in the description itself — the judging guidelines cap completeness at 3 for this. It is a clear 3, not 2 (the 'what' is concrete, not vague) and not 4 (no 'when' at all, not even an implicit one).

Trigger Term Quality

'DOM clobbering', 'named HTML elements', 'JavaScript global variables', and 'CSP' are natural phrases a user would say when they need this skill. A few common synonyms are missing (e.g., 'HTML injection', 'window globals', 'window.name'), so it falls just short of the comprehensive synonym coverage of the 5-anchor.

Distinctiveness Conflict Risk

'DOM clobbering' is a well-defined niche with distinct trigger terminology; no other skill would naturally claim these phrases. Minor adjacency to general XSS/CSP skills exists, but the term itself is unambiguous, matching the clear-niche 5-anchor.