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Fix lint workflow failing on fork PRs #5094

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Merged
kenyonj merged 4 commits into from
Mar 30, 2026
Merged

Fix lint workflow failing on fork PRs #5094

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f5d091f
Fix lint workflow for fork PRs
kenyonj Mar 30, 2026
1cc71e4
Fix CodeQL code injection warning
kenyonj Mar 30, 2026
41bdbef
Split lint into two jobs for security
kenyonj Mar 30, 2026
49fa487
Disable bundler cache in fork-facing lint job
kenyonj Mar 30, 2026
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30 changes: 25 additions & 5 deletions .github/workflows/lint.yml
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Original file line number Diff line number Diff line change
Expand Up @@ -5,13 +5,34 @@
workflow_dispatch:
merge_group:

permissions:
contents: write
checks: write

jobs:
lint:
runs-on: ubuntu-latest
permissions:
contents: read
steps:
- uses: actions/[email protected]
with:
ref: ${{ github.event.pull_request.head.sha || github.ref }}
repository: ${{ github.event.pull_request.head.repo.full_name || github.repository }}

Comment on lines 14 to 18
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Copilot AI Mar 30, 2026

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Using pull_request_target while checking out github.event.pull_request.head.sha from head.repo.full_name means the job will execute untrusted fork code with the base repo’s GITHUB_TOKEN permissions (contents: write at the workflow level). This is a known security footgun: a malicious fork PR can run arbitrary code (e.g., via Bundler/RuboCop) and use the write-scoped token to modify the base repository. Consider splitting into two jobs/workflows: a fork-safe lint job (triggered by pull_request or with job-level permissions: contents: read and no pushing) and a same-repo auto-correct job (only when head.repo.full_name == github.repository) that has write permissions and does the commit/push.

This issue also appears in the following locations of the same file:

  • line 18
  • line 44

Copilot uses AI. Check for mistakes.
- name: Setup Ruby
uses: ruby/[email protected]
with:
bundler-cache: false

- name: Install dependencies

Check failure

Code scanning / CodeQL

Cache Poisoning via execution of untrusted code High

Potential cache poisoning in the context of the default branch due to privilege checkout of untrusted code. (
pull_request_target
Loading
).
Comment on lines +19 to +24
run: bundle install

- name: Run RuboCop

Check failure

Code scanning / CodeQL

Cache Poisoning via execution of untrusted code High

Potential cache poisoning in the context of the default branch due to privilege checkout of untrusted code. (
pull_request_target
Loading
).
Comment on lines +24 to +27
run: |
bundle exec rubocop

autocorrect:

Check failure

Code scanning / CodeQL

Cache Poisoning via execution of untrusted code High

Potential cache poisoning in the context of the default branch due to privilege checkout of untrusted code. (
pull_request_target
Loading
).
Comment on lines +27 to +31
if: github.event.pull_request.head.repo.full_name == github.repository
runs-on: ubuntu-latest
permissions:
contents: write
steps:
- uses: actions/[email protected]
with:
Expand All @@ -27,7 +48,6 @@
bundle exec rubocop -A

- name: Check for changes
id: changes
run: |
git config --global user.name "github-actions[bot]"
git config --global user.email "github-actions[bot]@users.noreply.github.com"
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