* kube-apiserver: requests to endpoints handled by unavailable extension API servers (as indicated by an `Available` condition of `false` in the registered APIService) now return `503` errors instead of `404` errors. ([#58070](https://github.com/kubernetes/kubernetes/pull/58070), [@weekface](https://github.com/weekface))

## Changes by Kind

### Bug or Regression

- Fix an ephemeral port exhaustion bug caused by improper connection management that occurred when a large number of objects were handled by kubectl while exec auth was in use. ([#112339](https://github.com/kubernetes/kubernetes/pull/112339), [@enj](https://github.com/enj)) [SIG API Machinery and Auth]

- 'Container `preStop` and `postStart` lifecycle handlers using `httpGet` now
  honor the specified `scheme` and `headers` fields. This enables setting custom
  headers and changing the scheme to `HTTPS`, consistent with container
  startup/readiness/liveness probe capabilities. Lifecycle handlers configured
  with `scheme: HTTPS` that encounter errors indicating the endpoint is actually

### Bug or Regression

- Fix an ephemeral port exhaustion bug caused by improper connection management that occurred when a large number of objects were handled by kubectl while exec auth was in use. ([#112337](https://github.com/kubernetes/kubernetes/pull/112337), [@enj](https://github.com/enj)) [SIG API Machinery and Auth]

- Added `auditAnnotations` to `ValidatingAdmissionPolicy`, enabling CEL to be used to add audit annotations to request audit events.
  Added `validationActions` to `ValidatingAdmissionPolicyBinding`, enabling validation failures to be handled by any combination of the warn, audit and deny enforcement actions. ([#115973](https://github.com/kubernetes/kubernetes/pull/115973), [@jpbetz](https://github.com/jpbetz))

can now register for a single version of a resource (for example, `apps/v1 deployments`) and be called when any other version of that resource is modified (for example `extensions/v1beta1 deployments`). This allows new versions of a resource to be handled by admission webhooks without needing to update every webhook to understand the new version. See the API documentation for the `matchPolicy: Equivalent` option in MutatingWebhookConfiguration and ValidatingWebhookConfiguration types. ([#78135](ht...

- The 404 request handler for the GCE Ingress load balancer now exports prometheus metrics, including:

  - `http_404_request_total` (the number of 404 requests handled)
  - `http_404_request_duration_ms` (the amount of time the server took to respond in ms)

   3. KMS Provider's endpoint (path to Unix socket) is now validated when the EncryptionConfiguration files is loaded. This used to be handled by the GRPCService.

### Other notable changes

* Cluster Autoscaler 1.0.0 ([#53005](https://github.com/kubernetes/kubernetes/pull/53005), [@mwielgus](https://github.com/mwielgus))
* Remove the --docker-exec-handler flag. Only native exec handler is supported. ([#52287](https://github.com/kubernetes/kubernetes/pull/52287), [@yujuhong](https://github.com/yujuhong))

    * clusters. When that var is set to true, the command line flag enabling kubelet
    * client certificate rotation will be added to the kubelet command line.
* Make sure that resources being updated are handled correctly by Quota system ([#52452](https://github.com/kubernetes/kubernetes/pull/52452), [@gnufied](https://github.com/gnufied))