CVE-2026-76847 act 0.2.81 through 0.2.89 Missing Authorization in the Artifacts V4 Backend

act starts an HTTP Artifacts V4 backend whenever a workflow uses actions/upload-artifact@v4 or actions/download-artifact@v4. The control-plane RPCs of that backend, including CreateArtifact, GetSignedArtifactURL, ListArtifacts, FinalizeArtifact and DeleteArtifact, accept a caller-supplied...