* [prometheus-to-sd addon] Bump prometheus-to-sd to 0.3.1 to pick up security fixes, bug fixes and new features.
    * [event-exporter addon] Bump event-exporter to 0.2.3 to pick up security fixes.
* Fix validation for HealthzBindAddress in kube-proxy when --healthz-port is set to 0 ([#66138](https://github.com/kubernetes/kubernetes/pull/66138), [@wsong](https://github.com/wsong))

- Kubelet now exports a `server_expiration_renew_failure` and `client_expiration_renew_failure` metric counter if the certificate rotations cannot be performed. ([#84614](https://github.com/kubernetes/kubernetes/pull/84614), [@rphillips](https://github.com/rphillips))...

    * [prometheus-to-sd addon] Bump prometheus-to-sd to 0.3.1 to pick up security fixes, bug fixes and new features.
    * [event-exporter addon] Bump event-exporter to 0.2.3 to pick up security fixes.

- Export `NewDebuggingRoundTripper` function and `DebugLevel` options in the k8s.io/client-go/transport package. ([#98324](https://github.com/kubernetes/kubernetes/pull/98324), [@atosatto](https://github.com/atosatto))

- Enable external plugins can be used as subcommands for kubectl create command if subcommand does not exist as builtin only when KUBECTL_ENABLE_CMD_SHADOW environment variable is exported. ([#116293](https://github.com/kubernetes/kubernetes/pull/116293), [@ardaguclu](https://github.com/ardaguclu))

### Action Required

* New GCE or GKE clusters created with `cluster/kube-up.sh` will not enable the legacy ABAC authorizer by default. If you would like to enable the legacy ABAC authorizer, export ENABLE_LEGACY_ABAC=true before running `cluster/kube-up.sh`. ([#51367](https://github.com/kubernetes/kubernetes/pull/51367), [@cjcullen](https://github.com/cjcullen))

### Other notable changes

### SIG Cloud Provider

- The cloudstack cloud provider now reports a `Hostname` address type for nodes based on the `local-hostname` metadata key. ([#67719](https://github.com/kubernetes/kubernetes/pull/67719), [@liggitt](https://github.com/liggitt))

    * [prometheus-to-sd addon] Bump prometheus-to-sd to 0.3.1 to pick up security fixes, bug fixes and new features.
    * [event-exporter addon] Bump event-exporter to 0.2.3 to pick up security fixes.

- Exposes and sets a default timeout for the SubjectAccessReview client for DelegatingAuthorizationOptions ([#96153](https://github.com/kubernetes/kubernetes/pull/96153), [@p0lyn0mial](https://github.com/p0lyn0mial)) [SIG API Machinery and Cloud Provider]

* The behavior of the default handler for 404 requests fro the GCE Ingress load balancer is slightly modified in the sense that it now exports metrics using prometheus. The metrics exported include:  ([#79106](https://github.com/kubernetes/kubernetes/pull/79106), [@vbannai](https://github.com/vbannai))
    * - http_404_request_total  (the number of 404 requests handled)