([#57926](https://github.com/kubernetes/kubernetes/pull/57926), [@wwwtyro](https://github.com/wwwtyro))

* Check for known manifests during preflight instead of only checking for non-empty manifests directory. This makes the preflight checks less heavy-handed by specifically checking for well-known files (kube-apiserver.yaml, kube-controller-manager.yaml, kube-scheduler.yaml, etcd.yaml) in /etc/kubernetes/manifests instead of simply checking for a non-empty directory. ([#57287](https://github.com/kube...

Kubernetes releases are now generating provenance attestation files describing the staging and release phases of the release process and artifacts are verified as they are handed over from one phase to the next.
This final piece completes the work needed to comply with Level 1 of the [SLSA security framework](https://slsa.dev/) (Supply-chain Levels for Software Artifacts).