A security review guide for finding DOM-based cross-site scripting, where unsafe JavaScript puts attacker-controlled web-page data into code or HTML.

Use it to check web applications for unsafe uses of document.write, innerHTML, eval, location.href, setTimeout, and similar code paths.

It helps identify cases where browser input such as a URL fragment reaches dangerous JavaScript functions without being cleaned first.

dom-xss — Skill for Claude Code by securityfortech/hacking-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 securityfortech/hacking-skills --skill dom-xss

Clone the repo

git clone --depth 1 https://github.com/securityfortech/hacking-skills

Made for: Claude Code.

Or install web, the plugin that ships this one along with the rest of its 28 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/securityfortech/hacking-skills/dom-xss/github.svg)](https://agentmods.dev/skills/securityfortech/hacking-skills/dom-xss)

Your own site

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

Per session 117 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.

When invoked 1,841 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.

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	$0.00117	$0.01841
Opus 5.5	$0.00047	$0.00736
Sonnet 5.5	$0.00023	$0.00368
Haiku 4.5	$0.00012	$0.00184

Measured 2mo ago against content hash e24bc660f910, method: parsed. Prices are Anthropic first-party input rates as of 2026-10-07, from the pricing page.

Security

Grade A, and why

dom-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 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.

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.

skills/web/client-side/dom-xss/SKILL.md · 126 lines

The source is not reproduced here

No licence file

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 · 126 lines · 117 tokens per session scan A e24bc660f910

Subscribe to this mod's changes

dom-xss is a skill published in the GitHub repository securityfortech/hacking-skills (21 stars, last pushed 7mo ago), with no licence file. It adds 117 tokens to every session and 1,841 once invoked, about $0.0005 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.