Coordinated Disclosure Timeline
- 2021-01-18: Issue reported to maintainers
- 2021-02-23: Issue fixed
Summary
The surge-preview.yml GitHub workflow is vulnerable to unauthorized modification of the base repository or secrets exfiltration from a Pull Request.
Product
actions-cool/issues-helper GitHub repository
Tested Version
The latest changeset surge-preview.yml to the date.
Details
Issue: Untrusted code is explicitly checked out and run on a Pull Request from a fork
Workflows triggered on pull_request_target have read/write tokens for the base repository and the access to secrets. By explicitly checking out and running the build script from a fork the untrusted code is running in an environment that is able to push to the base repository and to access secrets. More details can be found in the article Keeping your GitHub Actions and workflows secure: Preventing pwn requests.
on: pull_request_target
...
- uses: actions/checkout@v2
with:
ref: refs/pull/${{ github.event.pull_request.number }}/merge
- uses: afc163/surge-preview@v1
with:
surge_token: ${{ secrets.SURGE_TOKEN }}
github_token: ${{ secrets.GITHUB_TOKEN }}
build: |
yarn
yarn docs-dev:build
dist: docs-dist
teardown: 'true'
...
Impact
The vulnerability allows for unauthorized modification of the base repository and secrets exfiltration.
Credit
This issue was discovered and reported by GHSL team member @JarLob (Jaroslav Lobačevski).
Contact
You can contact the GHSL team at securitylab@github.com, please include a reference to GHSL-2021-008 in any communication regarding this issue.