- The `build-tag` flag is reintroduced to conversion-gen and defaulter-gen which allow users to inject custom build tag during code generation process. ([#128259](https://github.com/kubernetes/kubernetes/pull/128259), [@dinhxuanvu](https://github.com/dinhxuanvu))

- Kube-apiserver: Previously persisted `CustomResourceDefinition` objects with an invalid whitespace-only `caBundle` could serve requests that did not require conversion. ([#132514](https://github.com/kubernetes/kubernetes/pull/132514), [@tiffanny29631](https://github.com/tiffanny29631))

### Feature

- Parallelize calls to conversion webhooks when watching from etcd to prevent watchcache from lagging and helps clusters with slow conversion webhooks or transformers. 

* Add mechanism for Admission Webhooks to specify which version of AdmissionReview they support ([#74998](https://github.com/kubernetes/kubernetes/pull/74998), [@mbohlool](https://github.com/mbohlool))
    * Add mechanism for CRD Conversion Webhooks to specify which version of ConversionReview they support

## Changes by Kind

### Bug or Regression

- Fixes a regression in 1.27.0 that resulted in "missing metadata in converted object" errors when modifying objects for multi-version custom resource definitions with a conversion strategy of `None`. ([#117305](https://github.com/kubernetes/kubernetes/pull/117305), [@ncdc](https://github.com/ncdc)) [SIG API Machinery]

re-enable deprecated legacy behavior of treating the CommonName of X.509 serving certificates as a host name. This behavior has been disabled by default since 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_x5...

- Kubernetes 1.24 is built with go1.18, which will no longer validate certificates signed with a SHA-1 hash algorithm by default. See https://golang.org/doc/go1.18#sha1 for more details. If you are using certificates like this in admission or conversion ([#109024](https://github.com/kubernetes/kubernetes/pull/109024), [@stlaz](https://github.com/stlaz))