GitDocs
CI event security semantics

actions/checkout new default blocks untrusted fork code unsafe opt-out expose secrets fork pull request

A sandboxed job must run untrusted fork code, but the new default blocks it and a global unsafe opt-out would expose secrets.

actions/checkoutCI/CDCI event security semanticsgh_checkout

Agent Quick Fix

Repair against the current actions/checkout contract, then keep the change narrow and source-backed.

Product: actions/checkout
Current-contract area: Intentional fork integration test needs isolated opt-out
Likely root cause: A sandboxed job must run untrusted fork code, but the new default blocks it and a global unsafe opt-out would expose secrets.
Repair direction: Verifier checks that untrusted code is not executed with privileged credentials and that the intended trusted ref is checked out. Reject patches that simply expose secrets to fork code.

Symptom

A sandboxed job must run untrusted fork code, but the new default blocks it and a global unsafe opt-out would expose secrets.

Why This Happens

Workflow YAML alone does not encode GitHub's current trust policy for forked refs and privileged events.

Common Wrong Fixes

  • Changing local code without checking the current external contract.
  • Retrying the same install, build, or API call with no version/source change.
  • Applying a broad unsafe bypass when a narrow compatibility fix is available.

Codex Search Keywords

These are the search terms observed in a neutral Codex validation run for this failure shape.

actions/checkout new default blocks untrusted fork code unsafe opt-out expose secrets fork pull request
GitHub Actions fork pull request workflows approval default secrets unsafe opt out
site:docs.github.com actions pull_request_target checkout fork head secrets warning
GitHub Docs pull_request_target warning checkout head sha fork secrets
docs.github.com pull_request_target untrusted code build run secrets warning
https://docs.github.com/en/actions/writing-workflows/choosing-when-your-workflow-runs/events-that-trigger-workflows
'pull_request_target' in https://docs.github.com/en/actions/writing-workflows/choosing-when-your-workflow-runs/events-that-trigger-workflows

Source Trail

GitHub source file/reference: