GNU testsuite comparison:

Skip an intermittent issue tests/timeout/timeout (fails in this run but passes in the 'main' branch)

maybe it should be reported to upstream as a bug

FWIW, this is not a false positive: the impact is low in your case, but any third-party fork can declare a new foo.yml with name: GnuTests and trigger your workflow in an upstream context.

(In your case the attacker can run a workflow with upstream repo credentials, which they can then use to submit an arbitrary comment/contents as if it was your normal "testsuite comparison" response. This is pretty low-impact, but it's probably not something you intended 🙂)

Thanks for the information! If we were going to fix this what would we do?

My recommendation would be to switch from workflow_run to workflow_call -- there are some recommendations and links here: https://woodruffw.github.io/zizmor/audits/#remediation_1