- `kubectl rollout undo` now returns errors when attempting to rollback a deployment to a non-existent revision ([#70039](https://github.com/kubernetes/kubernetes/pull/70039), [@liggitt](https://github.com/liggitt))

- Kubeadm: during the validation of existing kubeconfig files on disk, handle cases where the "ca.crt" is a bundle and has intermediate certificates. Find a common trust anchor between the "ca.crt" bundle and the CA in the existing kubeconfig on disk instead of treating "ca.crt" as a file containing a single CA. ([#123102](https://github.com/kubernetes/kubernetes/pull/123102), [@as...

- Fixed bug that caused a resource to include patch directives when using strategic merge patch against a non-existent field. ([#117568](https://github.com/kubernetes/kubernetes/pull/117568), [@alexzielenski](https://github.com/alexzielenski))

*   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 to use the latest API. For this and the previous...

  - NetworkPolicy resources will no longer be served from `extensions/v1beta1` in v1.16. Migrate use to the `networking.k8s.io/v1` API, available since v1.8. Existing persisted data can be retrieved via the `networking.k8s.io/v1` API.

### Beta APIs Off by Default

[New beta APIs will not be enabled in clusters by default](https://github.com/kubernetes/enhancements/issues/3136).
Existing beta APIs and new versions of existing beta APIs, will continue to be enabled by default.

### Signing Release Artifacts

* Azure disks now support external resource groups.
([#64427](https://github.com/kubernetes/kubernetes/pull/64427), [@andyzhangx](https://github.com/andyzhangx))
* Added reason message logs for non-existent Azure resources.
([#64248](https://github.com/kubernetes/kubernetes/pull/64248), [@feiskyer](https://github.com/feiskyer))

### SIG CLI

- Reverted a kubectl azure auth module change where oidc claim spn: prefix was omitted resulting a breaking behavior with existing Azure AD OIDC enabled api-server ([#87507](https://github.com/kubernetes/kubernetes/pull/87507), [@weinong](https://github.com/weinong)) [SIG API Machinery, Auth and Cloud Provider]

empty cgroupDriver value in the KubeletConfiguration is now always set to "systemd" unless the user is explicit about it. This requires existing machine setups to configure the container runtime to use the "systemd" driver. Documentation on this topic can be found here: https://kubernetes.io/docs/setup/production-environment/container-runtimes/. When upgrading existing clusters / nodes using "kubeadm upgrade" the old cgroupDriver value is preserved, but in 1.22 this change will also apply to "upgrade"....

  - NetworkPolicy resources will no longer be served from `extensions/v1beta1` in v1.16. Migrate use to the `networking.k8s.io/v1` API, available since v1.8. Existing persisted data can be retrieved via the `networking.k8s.io/v1` API.