A skill for finding and testing cross-site scripting (XSS) vulnerabilities, where unwanted JavaScript is injected into a website.

Use it only for authorized testing of reflected, stored, DOM-based, or blind XSS in web applications.

It helps security testers check whether user-controlled values in URLs, forms, headers, or the page can execute injected scripts.

exploit-xss — Skill for Claude Code and Codex by crazyMarky

Install

Getting it into your agent

One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.

Any agent

npx skills add crazyMarky/pentest-skills --skill exploit-xss

Clone the repo

git clone --depth 1 https://github.com/crazyMarky/pentest-skills

Made for: Claude Code, Codex.

Wrote this? Show the measurements

A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.

README.md

[![agentmods](https://agentmods.dev/badge/skills/crazymarky/pentest-skills/exploit-xss/github.svg)](https://agentmods.dev/skills/crazymarky/pentest-skills/exploit-xss)

Your own site

<a href="https://agentmods.dev/skills/crazymarky/pentest-skills/exploit-xss"><img src="https://agentmods.dev/badge/skills/crazymarky/pentest-skills/exploit-xss/github.svg" alt="Measured on agentmods" height="20"></a>

Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.

Your own site · 80×15

<a href="https://agentmods.dev/skills/crazymarky/pentest-skills/exploit-xss"><img src="https://agentmods.dev/badge/skills/crazymarky/pentest-skills/exploit-xss.svg" alt="Reviewed on agentmods" width="80" height="20"></a>

Per session 71 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.

When invoked 5,576 The whole file, excluding the scripts and references it only reads on demand.

Security scan A 0 findings. A grade says what 26 rules found in the file — not that it is safe. Third-party audits

NVIDIA SkillSpector warn 7 Sept 2026

SkillSpector: 1 finding, up to high

These are SkillSpector’s own severities. On a checked sample its high-severity flags on skills were ~96% false positives — a documented command, a public API, a “never do X” rule — so we show them as a caution to read, not a verdict. Why →

high YARA Match · line 183
YARA rule matched a hack tool or exploit indicator (offensive tools, reconnaissance, privilege escalation, or exploit frameworks).

Fix: Remove offensive tool references and exploit code. Legitimate agent skills should not contain penetration testing tools, exploit frameworks, or reconnaissance utilities.

How audits are shown

Origin original No closer match found in the catalogue.

Token cost

What it costs to keep this loaded

Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.

Model	Per session	Once invoked
Fable 5.1	$0.00071	$0.05576
Opus 5.5	$0.00028	$0.02230
Sonnet 5.5	$0.00014	$0.01115
Haiku 4.5	$0.00007	$0.00558

Measured 1mo ago against content hash 6304f9a63ac0, method: parsed. Prices are Anthropic first-party input rates as of 2026-10-07, from the pricing page.

Security

Grade A, and why

exploit-xss scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 1mo ago.

The scan reads SKILL.md. This mod also ships 12 executable files (scripts/blind_xss_tester.py, scripts/csp_detector.py, scripts/framework_xss_tester.py, …), listed below but not scanned — reading those needs a real analyzer, not pattern matching.

A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.

Nothing flagged

None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.

exploit-xss/SKILL.md · 731 lines

How it starts

The opening of the file, as written. The whole thing — 731 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Cross-Site Scripting (XSS) Detection Skill

⚠️ DANGER - Authorization Required

This skill is for AUTHORIZED SECURITY TESTING ONLY.

You must have:

Written permission from the target system owner
Legal authorization to test the target
A defined scope of testing

Unauthorized XSS testing is ILLEGAL and unethical.

Prerequisites

Required Tools

# XSStrike - Advanced XSS scanner with DOM support
pip install xsstrike
# Or: git clone https://github.com/s0md3v/XSStrike

# Dalfox - Fast XSS scanner with pipeline mode
go install github.com/hahwul/dalfox/v2@latest

# XSpear - XSS testing with WAF bypass
gem install xspear

Python Requirements

# Install required Python packages for built-in scripts
pip install requests beautifulsoup4

# Optional: WebSocket XSS testing
pip install websockets

Optional Tools

# Burp Suite for manual testing
# OWASP ZAP for automated scanning

Quick Start

Basic URL Testing

# Test a URL parameter for XSS
python xsstrike.py -u "https://target.com/search?q=test"

# Fast scanning with Dalfox
dalfox url "https://target.com/search?q=test"

POST Request Testing

# Save POST request to file
dalfox file request.txt

# Or use XSStrike
python xsstrike.py -r request.txt

DOM XSS Testing

# DOM XSS with XSStrike
python xsstrike.py -u "https://target.com/page#test" --dom

# DOM XSS with Dalfox
dalfox url "https://target.com/page#test" --dom

Common Scenarios

1. Basic Parameter Testing (Reflected XSS)

Test URL parameters for reflection and injection:

# Single URL testing
python xsstrike.py -u "https://target.com/search?q=test"

# Dalfox for faster scanning
dalfox url "https://target.com/search?q=test"

# Specify parameter
dalfox url "https://target.com/search" -p q

What to check:

Does the input reflect in the HTML response?
What is the context (HTML tag, attribute, JavaScript)?
Are there any filters/encoding applied?

Read the full file on GitHub · 731 lines

Files

What ships with it

40 files beside SKILL.md in the same directory: the scripts, references and assets a skill reads on demand. Not counted in the per-session cost; read them before you install if any of them is executable.

Changes

What this file has done since we first saw it

Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.

1mo ago First seen · 731 lines · 71 tokens per session scan A 6304f9a63ac0

Subscribe to this mod's changes

exploit-xss is a skill published in the GitHub repository crazyMarky/pentest-skills (341 stars, last pushed 4mo ago), licensed Apache-2.0. It adds 71 tokens to every session and 5,576 once invoked, about $0.0003 per session on Opus 5.5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.

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