*   The admission webhook configurations API, part of the admissionregistration API, is now at v1beta1. Delete any existing webhook configurations before you upgrade, and update your configuration files...

  - When registering with a 1.17+ API server, a CustomResourceDefinition conversion webhook can now request that only `v1` ConversionReview requests be sent to them. Previously, conversion webhooks were required to support receiving `v1beta1` ConversionReview requests as well for...

#tokenreview-v1-authentication-k8s-io) for the new tokens for improved scoping. Under audit logging, the new alpha-level "dynamic audit configuration" adds support for [dynamically registering webhooks to receive a stream of audit events](https://kubernetes.io/docs/tasks/debug/debug-cluster/audit/#webhook-backend). Finally, we've enhanced secrets protection by graduating [etcd encryption](https://kubernetes.io/docs/tasks/administer-cluster/encrypt-data/) out of experimental.

### SIG...

Kubernetes 1.19 / go 1.15. Serving certificates used by admission webhooks, custom resource conversion webhooks, and aggregated API servers must now include valid Subject Alternative Names. If you are running Kubernetes 1.22 with `GODEBUG=x509ignoreCN=0` set, check the `apiserver_kube_aggregator_x509_missing_san_total` and `apiserver_webhooks_x509_missing_san_total` metrics for non-zero values to see if the API server is connecting to webhooks or aggregated API servers using certificates that will be considered...

- Fixed an issue where the API server did not send impersonated UID to authentication webhooks. ([#116681](https://github.com/kubernetes/kubernetes/pull/116681), [@stlaz](https://github.com/stlaz)) [SIG API Machinery and Auth]

* The webhook admission plugin now works even if the API server and the nodes are in two separate networks,for example, in GKE.
The webhook admission plugin now lets the webhook author use the DNS name of the service as the CommonName when generating the server cert for the webhook.
Action required:

- Kube-apiserver: Authorization webhooks now report the following metrics:
  - apiserver_authorization_webhook_evaluations_total
  - apiserver_authorization_webhook_duration_seconds

### CVE-2021-25735: Validating Admission Webhook does not observe some previous fields

A security issue was discovered in kube-apiserver that could allow node
updates to bypass a Validating Admission Webhook. You are only affected
by this vulnerability if you run a Validating Admission Webhook for Nodes
that denies admission based at least partially on the old state of the
Node object.

- APIServerTracing now collects spans from outgoing requests to admission webhooks. ([#103601](https://github.com/kubernetes/kubernetes/pull/103601), [@dashpole](https://github.com/dashpole)) [SIG API Machinery]
- Add a namespace label for all `apiserver_admission_* metrics`.

* [alpha] Adding admissionregistration API group which enables dynamic registration of initializers and external admission webhooks. ([#46294](https://github.com/kubernetes/kubernetes/pull/46294), [@caesarxuchao](https://github.com/caesarxuchao))


### **Application Deployment**
#### StatefulSet