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What the check does

Flags dependency caching — actions/cache, or a setup-* action’s cache: option — in a workflow that also publishes a release-shaped artifact (release upload, container push, npm/cargo/gem publish, GoReleaser, …). This is broader than SLSA-BUILD-L3 cache poisoning, which only covers a pull_request_target cache key built from PR-controlled input.

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Why it matters

GitHub Actions caches are shared across a repository’s workflows and branches. A lower-trust workflow (for example one triggered by a fork’s pull request) can write a cache entry that a later, higher-trust publishing run restores — and the poisoned content flows straight into the released artifact. Because the cache is keyed by content the attacker can influence, this is a supply-chain path that SHA-pinning your actions does not close.

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Safe alternative

Keep the publishing path from restoring a mutable cache:
Or drop the cache entirely on release builds, and scope caching to the non-publishing CI workflow.