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xss

Cross-Site Scripting (XSS) — reflected, stored, DOM-based XSS exploitation. Covers filter bypass, CSP evasion, bot-triggered cookie exfiltration, admin page scraping, and headless browser flag extraction. Use for any challenge involving client-side JavaScript injection, Cross payloads, cookie theft, or browser-based exploitation.

Quality

86%

Does it follow best practices?

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SecuritybySnyk

Critical

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SKILL.md
Quality
Evals
Security

Quality

Content

77%Weight 40%Scale 1-5

Reviews the quality of instructions and guidance provided to agents. Good implementation is clear, handles edge cases, and produces reliable results.

Highly actionable, executable guidance with strong workflow sequencing, validation checkpoints, and explicit budget/convergence rules tailored to the challenge environment. The weaknesses are redundancy — three overlapping filter-bypass sections with conflicting iteration caps — and no progressive disclosure: ~290 lines of payload reference material are inlined in a single file rather than split into a reference document.

Suggestions

Consolidate 'Filter Bypass Techniques', 'Filter Bypass Cookbook', and 'Bypass-Class Rotation Rule' into one section — their payload lists substantially overlap, and the pivot rule (≤3 per class) conflicts with the rotation rule (≤2 per class), so state a single iteration budget.

Move the bypass-class rotation table and the JSFuck deep-dive into a references/ file (e.g., references/payloads.md), keeping SKILL.md to the pattern-detection decision, core workflow, and convergence rules so the always-loaded context is much smaller.

Reconcile the two Cross-series stopping rules ('5 filter bypass attempts' in the Budget Cap section vs '≥4 classes tried 2×' in the Rotation Rule section) into one unambiguous termination condition.

DimensionReasoningScore

Conciseness

The body is command-dense with no basic-concept padding (no 'what is XSS' explanations), but filter-bypass material is duplicated across three sections ('Filter Bypass Techniques', 'Filter Bypass Cookbook', 'Bypass-Class Rotation Rule') and iteration-budget rules are stated twice with conflicting limits (pivot rule: ≤3 payloads per class; rotation rule: ≤2 per class). Not 4 because this redundancy is more than minor trimming; not 2 because the bulk is novel environment-specific guidance, not generic explanation.

3 / 5

Actionability

Fully executable throughout: copy-paste curl probes with exact grep success conditions, ready-to-run JSFuck node one-liners with a verification step for alphanumeric content, URL-encoding helpers, and payload tables covering both the bot-exfiltration and server-side-alert patterns. Not 4: even edge cases (TypeError fallback, partial-range filter probing) come with concrete commands rather than hints.

5 / 5

Workflow Clarity

Clear sequencing with explicit validation checkpoints: pattern identification first (with a quick curl discriminator), an 8-step numbered workflow, listener verification, response grep checks, and error-recovery feedback loops (JSFuck TypeError → runInParentScope fallback → raw eval wrap). Hard convergence rules with a documented stop condition prevent runaway iteration. Not 4: both checkpoints and recovery loops are explicit and complete.

5 / 5

Progressive Disclosure

Good section structure with clear ## headers and navigable tables, but the ~290-line body inlines substantial reference material (bypass cookbook, 8-class rotation table, JSFuck deep-dive) that belongs in a references file, so everything loads into context on every invocation. Not 2 because the sections are well-organized and nothing is buried; not 4 because a file this size clearly warrants splitting core workflow from payload reference material.

3 / 5

Total

16

/

20

Passed

Description

92%Weight 40%Scale 1-5

Based on the skill's description, can an agent find and select it at the right time? Clear, specific descriptions lead to better discovery.

A strong description: concrete capability enumeration across all XSS variants plus an explicit, well-phrased 'Use when' trigger clause. The only weakness is that a handful of natural trigger synonyms live in metadata.when_to_use rather than the description text itself.

DimensionReasoningScore

Specificity

The description lists multiple concrete actions — 'filter bypass, CSP evasion, bot-triggered cookie exfiltration, admin page scraping, and headless browser flag extraction' — across all three XSS classes ('reflected, stored, DOM-based'), giving comprehensive coverage rather than 1-2 actions. Not the level below (4) because coverage has no notable gaps; no anchor above exists.

5 / 5

Completeness

Explicitly answers both: what ('reflected, stored, DOM-based XSS exploitation... filter bypass, CSP evasion, bot-triggered cookie exfiltration') and when ('Use for any challenge involving client-side JavaScript injection, Cross payloads, cookie theft, or browser-based exploitation') with concrete trigger phrases — a direct match to the score-5 anchor. Not 4, since the 'when' clause is fully explicit rather than improvable.

5 / 5

Trigger Term Quality

Good natural keyword coverage — 'Cross-Site Scripting (XSS)', 'client-side JavaScript injection', 'cookie theft', 'Cross payloads', 'browser-based exploitation' — the phrases a user would naturally say. Falls short of 5 because a few common variations users would blurt ('script injection', 'alert', 'cookie steal') appear only in metadata.when_to_use, not in the description itself.

4 / 5

Distinctiveness Conflict Risk

Clear niche — CTF browser-side JavaScript exploitation — with distinct triggers ('Cross payloads', 'bot-triggered cookie exfiltration', 'headless browser flag extraction') unlikely to fire for adjacent web-exploitation skills. Not 4: there is no meaningful overlap risk with closely related skills given the specific trigger vocabulary.

5 / 5

Total

19

/

20

Passed

Validation

87%

Checks the skill against the spec for correct structure and formatting. All validation checks must pass before discovery and implementation can be scored.

Validation — 14 / 16 Passed

Validation for skill structure

CriteriaDescriptionResult

metadata_version

'metadata.version' is missing

Warning

relative_links

Relative link issues: 3 missing

Warning

Total

14

/

16

Passed

Repository

PurpleAILAB/Decepticon

Path

packages/decepticon/decepticon/skills/standard/exploit/web/xss/SKILL.md

Reviewed

Table of Contents

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