The dangerci.yml GitHub workflow is vulnerable to unauthorized modification of the base repository or secrets exfiltration from a Pull Request.
Automattic/jetpack GitHub repository
The latest changeset 1bc2f22 to the date.
pull_request_target
was introduced to allow triggered workflows to comment on PRs, label them, assign people, etc.. In order to make it possible the triggered action runner has read/write token for the base repository and the access to secrets. In order to prevent untrusted code from execution it runs in a context of the base repository.
By explicitly checking out and running 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.
on: pull_request_target
env:
DANGER_GITHUB_API_TOKEN: ${{ secrets.DANGER_TOKEN }}
...
- uses: actions/checkout@v2
with:
ref: ${{ github.event.pull_request.head.ref }}
repository: ${{ github.event.pull_request.head.repo.full_name }}
...
- run: |
yarn install
yarn danger ci
...
The vulnerability allows for unauthorized modification of the base repository and secrets exfiltration.
This issue was discovered and reported by GHSL team member @JarLob (Jaroslav Lobačevski).
You can contact the GHSL team at [email protected]
, please include a reference to GHSL-2020-329
in any communication regarding this issue.