etes-api/migrate-third-party-resource/).

* [beta] User-provided apiservers can be aggregated (served along with) the rest of the Kubernetes API. See [Extending the Kubernetes API with the aggregation layer](https://kubernetes.io/docs/concepts/api-extension/apiserver-aggregation/), [Configure the aggregation layer](https://kubernetes.io/docs/tasks/access-kubernetes-api/configure-aggregation-layer/), and [Setup an extension API server](https://kubernetes.io/docs/tasks/access-kubernete...

### Auth

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 invalid in Kubernetes 1.23+....

* Support OpenAPI spec aggregation for kube-aggregator ([#46734](https://github.com/kubernetes/kubernetes/pull/46734), [@mbohlool](https://github.com/mbohlool))

  - [Changelog since v1.25.0](#changelog-since-v1250)
  - [Important Security Information](#important-security-information-4)
    - [CVE-2022-3172: Aggregated API server can cause clients to be redirected (SSRF)](#cve-2022-3172-aggregated-api-server-can-cause-clients-to-be-redirected-ssrf)
  - [Changes by Kind](#changes-by-kind-14)
    - [API Change](#api-change-3)
    - [Feature](#feature-13)

  - [Changelog since v1.24.4](#changelog-since-v1244)
  - [Important Security Information](#important-security-information-3)
    - [CVE-2022-3172: Aggregated API server can cause clients to be redirected (SSRF)](#cve-2022-3172-aggregated-api-server-can-cause-clients-to-be-redirected-ssrf)

- The `horizontalpodautoscaling` and `clusterrole-aggregation` controllers now assume the `autoscaling/v1` and `rbac.authorization.k8s.io/v1` APIs are available. If you disable those APIs and do not want to run those controllers, exclude them by passing `--controllers=-horizontalpodautoscaling` or `--controllers=-clusterrole-aggregation` to `kube-controller-manager`. ([#117977](https://github.com/kubernetes/kubernetes/pull/117977), [@liggit...

* corrects a race condition in bootstrapping aggregated cluster roles in new HA clusters ([#63761](https://github.com/kubernetes/kubernetes/pull/63761), [@liggitt](https://github.com/liggitt))

### SIG Auth

Work this cycle focused on graduating existing functions, and on making security functions more understandable for users.

- NONE ([#124326](https://github.com/kubernetes/kubernetes/pull/124326), [@ritazh](https://github.com/ritazh)) [SIG Auth]
- OpenAPI V2 will no longer publish aggregated apiserver OpenAPI for group-versions not matching the APIService specified group version ([#123625](https://github.com/kubernetes/kubernetes/pull/123625), [@Jefftree](https://github.com/Jefftree)) [SIG API Machinery and Testing]