Artifact Poisoning POC

This repository demonstrates a GitHub Actions artifact poisoning vulnerability similar to the one found in sveltejs/svelte.

Vulnerability

The post-comment.yml workflow:

1. Triggers on workflow_run completion of build-artifact.yml
2. Downloads artifact created by the triggering workflow
3. Trusts artifact content to determine which issue/PR to comment on
4. Trusts artifact content for the comment body

Attack Vector

When a PR from a fork triggers build-artifact.yml:

• The fork's version of the workflow runs
• The fork can create a malicious artifact
• The post-comment.yml (running in main repo context with write permissions) downloads and trusts it

To Test

1. Fork this repository
2. Modify .github/workflows/build-artifact.yml in your fork
3. Open a PR to this repository
4. Observe the comment posted based on your artifact content