Fix check_task workflow failing on fork PRs - #2941
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…kout guard) actions/checkout now refuses to check out a fork PR's head commit inside a pull_request_target workflow unless explicitly opted in, since that combination (untrusted code + base-repo secrets/token) is the classic "pwn request" pattern. This broke check_task.yml for every fork PR (e.g. #2940). Split the workflow: the two jobs that don't need secrets (check-affected-files, check-pr-description) move to plain pull_request, which is inherently safe for fork code. The Canvas-updating job needs base-repo secrets so it stays on pull_request_target in its own file (check_task_canvas.yml) and explicitly opts in to the fork checkout, since it only reads the checked-out README and never executes anything from the fork's commit.
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Summary
check_task.ymlruns onpull_request_targetand checks out the PR's fork commit (github.event.pull_request.head.sha).actions/checkoutnow blocks that combination by default (checking out untrusted fork code into a privilegedpull_request_targetcontext is the "pwn request" pattern), which breaks the workflow for every fork PR — e.g. Scientific paper proposal: An Empirical Evaluation of Using Large Language Models for Automated Unit Test Generation, week 2 #2940.check-affected-filesandcheck-pr-description(no secrets used) move to plainpull_request, which is safe for fork code by design.check-canvasneedssecrets.CANVAS_TOKEN/GH_TOKENto update grading, so it must stay privileged. Moved it to its own workflow file (check_task_canvas.yml) onpull_request_target, withallow-unsafe-pr-checkout: trueexplicitly set — safe here since the job only reads the checked-out README to diff it and never executes anything from the fork's commit.