known-bad-skill

known-bad-skill is a skill for Claude Code, Codex from RudrenduPaul/skillguard. It costs 57 tokens per session (219 once invoked), scanned A, original, Apache-2.0.

A deliberately vulnerable-looking test skill used by SkillGuard, a tool for checking skills for security findings. It is an inert fixture and is not intended for real agent use.

In plain words
What is it for?
Use it only to test a SkillGuard scan and verify that the scanner reports file-and-line security findings.
Why use it?
It provides safe sample input for demos and end-to-end tests of SkillGuard’s detection rules.

Skill for Claude CodeCodex

Written for no agent in particular: nothing here depends on one.

Good fit Use it only to test a SkillGuard scan and verify that the scanner reports file-and-line security findings.

Compare 6 skills from other repositories ↓
Install with agentmods
npx agentmods add skills/rudrendupaul/skillguard/known-bad-skill
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 RudrenduPaul/skillguard --skill known-bad-skill
Clone the repo
git clone --depth 1 https://github.com/RudrenduPaul/skillguard

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 known-bad-skill

README.md
[![agentmods](https://agentmods.dev/badge/skills/rudrendupaul/skillguard/known-bad-skill/github.svg)](https://agentmods.dev/skills/rudrendupaul/skillguard/known-bad-skill)
Your own site
<a href="https://agentmods.dev/skills/rudrendupaul/skillguard/known-bad-skill"><img src="https://agentmods.dev/badge/skills/rudrendupaul/skillguard/known-bad-skill/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 known-bad-skill

Your own site · 80×15
<a href="https://agentmods.dev/skills/rudrendupaul/skillguard/known-bad-skill"><img src="https://agentmods.dev/badge/skills/rudrendupaul/skillguard/known-bad-skill.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 57 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 219 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 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.

ModelPer sessionOnce invoked
Fable 5.1 $0.00057 $0.00219
Opus 5 $0.00028 $0.00110
Sonnet 5 $0.00011 $0.00044
Haiku 4.5 $0.00006 $0.00022

Measured 10d ago against content hash 51f43d524d6a, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-10, from the pricing page.

Security

Grade A, and why

known-bad-skill 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 10d ago.

The scan reads SKILL.md. This mod also ships 5 executable files (hooks/backdoor.py, hooks/cleanup.sh, hooks/install.sh, …), 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.

examples/known-bad-skill/SKILL.md · 29 lines

What it actually says

Known Bad Skill (fixture)

This is a synthetic, deliberately vulnerable-looking skill bundled with SkillGuard for demos and end-to-end tests. Every script under hooks/ is inert: none of it is ever executed by SkillGuard, by npm install, or by any other process in this repository. The domains referenced use the .invalid TLD reserved by RFC 2606, so even a stray manual execution would resolve nothing.

Run:

npx skillguard-cli scan ./examples/known-bad-skill

to see SkillGuard flag it, including at least one HIGH-severity, file:line-cited finding.

Files

What ships with it

5 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.

  1. 10d ago First seen · 29 lines · 57 tokens per session scan A 51f43d524d6a

Subscribe to this mod's changes

known-bad-skill is a skill published in the GitHub repository RudrenduPaul/skillguard (1 stars, last pushed today), licensed Apache-2.0. It adds 57 tokens to every session and 219 once invoked, about $0.0003 per session on Opus 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 2026-08-31.

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