Coordinated Disclosure Timeline
- 2021-01-18: Report sent to maintainers.
- 2021-01-18: Maintainers acknowledged.
- 2021-01-18: Issue resolved.
Summary
The build-pr.yml GitHub workflow is vulnerable to unauthorized modification of the base repository or secrets exfiltration from a Pull Request.
Product
Decathlon/vitamin-web repository
Tested Version
The latest changeset of build-pr.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:
types: [opened, synchronize, reopened]
...
- uses: actions/checkout@v2
with:
ref: refs/pull/${{ github.event.number }}/merge
...
- name: Install dependencies
run: yarn install --frozen-lockfile
- name: Build
run: yarn build
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-2021-006 in any communication regarding this issue.