prompt-injection-audit

prompt-injection-audit is a skill for Claude Code, Codex from forefy/.context. It costs 55 tokens per session (1,963 once invoked), scanned A, original, MIT.

A security testing procedure for finding indirect prompt injection in an AI application. It sends crafted instructions through the data channels the agent reads and checks whether they cause unintended actions.

In plain words
What is it for?
Use it to profile an AI agent, test different injection techniques and delivery channels, verify impact with an out-of-band callback, and record false positives and results.
Why use it?
It helps reveal when outside content can override an agent's instructions, while requiring authorization because the test may make the agent act through its tools.

Skill for Claude CodeCodex

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

Good fit Use it to profile an AI agent, test different injection techniques and delivery channels, verify impact with an out-of-band callback, and record false positives and results.

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Install with agentmods
npx agentmods add skills/forefy/.context/prompt-injection-audit
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 forefy/.context --skill prompt-injection-audit
Clone the repo
git clone --depth 1 https://github.com/forefy/.context

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 prompt-injection-audit

README.md
[![agentmods](https://agentmods.dev/badge/skills/forefy/.context/prompt-injection-audit/github.svg)](https://agentmods.dev/skills/forefy/.context/prompt-injection-audit)
Your own site
<a href="https://agentmods.dev/skills/forefy/.context/prompt-injection-audit"><img src="https://agentmods.dev/badge/skills/forefy/.context/prompt-injection-audit/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 prompt-injection-audit

Your own site · 80×15
<a href="https://agentmods.dev/skills/forefy/.context/prompt-injection-audit"><img src="https://agentmods.dev/badge/skills/forefy/.context/prompt-injection-audit.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 55 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 1,963 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 $0.00055 $0.01963
Opus 5 $0.00028 $0.00981
Sonnet 5 $0.00011 $0.00393
Haiku 4.5 $0.00006 $0.00196

Measured 4d ago against content hash 6cecedb9f6d9, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-12, from the pricing page.

Security

Grade A, and why

prompt-injection-audit 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 4d 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/llms/prompt-injection-audit/SKILL.md · 119 lines

How it starts

The opening of the file, as written. The whole thing — 119 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Contents

  • Scope & authorization (blast-radius labels)
  • Model endpoint or agent application: when to use a scanner instead
  • Phase 0 - target profile: what is even reachable
  • Phase 1 - oracle and channel setup, with the canary gate
  • Phase 2 - technique-family triage
  • Phase 3 - matrix run
  • Phase 4 - judged objectives
  • False-positive gates
  • Output
  • Reference files: references/technique-matrix.md, references/delivery-channels.md, references/results-schema.md

Scope & authorization

Only run against an LLM application you own or are contractually engaged to test. This skill makes a target agent take actions its operator did not intend, so the authorization has to name the agent, its tools, and the accounts it acts as - not just the web app in front of it.

Blast-radius labels:

  • Passive (phase 0) - profiling. Reads the app's own surface and documentation.
  • Active-3rdparty (phase 1) - stands up a callback host and arms a channel. Payload content reaches your own infrastructure.
  • Active (phases 2-4) - the target agent executes injected instructions. Anything it can do, a landed payload can do.

Two objectives need their own sign-off before you run them. Memory poisoning persists past the engagement window and needs an agreed cleanup step. Token exhaustion is resource exhaustion against a metered service: get it in writing, cap it, run it off-peak, or skip it and record it as skipped.

Model endpoint or agent application

Decide this before anything else, because it decides whether this skill is the right instrument.

A raw model endpoint - you hold an API key and send prompts directly - is scanner work. Corpus scanners such as Praetorian's Augustus carry hundreds of probes across dozens of provider bindings and score them with maintained detectors. Point one at the endpoint and take the result. Do not hand-roll a corpus here; a payload library frozen in markdown goes stale against the next model revision, and breadth is not what a methodology skill adds.

Read the full file on GitHub · 119 lines

Files

What ships with it

3 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. 4d ago First seen · 119 lines · 55 tokens per session scan A 6cecedb9f6d9

Subscribe to this mod's changes

prompt-injection-audit is a skill published in the GitHub repository forefy/.context (146 stars, last pushed 3d ago), licensed MIT. It adds 55 tokens to every session and 1,963 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 2026-09-08.

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