- When registering with a 1.17+ API server, MutatingWebhookConfiguration and ValidatingWebhookConfiguration objects can now request that only `v1` AdmissionReview requests be sent to them. Previously, webhooks were required to support receiving `v1beta1` AdmissionReview requests as well for compatibility with API servers <= 1.15.

  - `admissionReviewVersions` default value is removed and the field made required for v1 (supported versions for AdmissionReview are `v1` and `v1beta1`)
  - The `name` field for specified webhooks must be unique for `MutatingWebhookConfiguration` and `ValidatingWebhookConfiguration` objects created via `admissionregistration.k8s.io/v1`

    * `admission/v1alpha1#AdmissionReview` now contains `AdmissionRequest` and `AdmissionResponse`. `AdmissionResponse` includes a `Patch` field to allow mutating webhooks to send json patch to the apiserver.

- CRI now supports a "runtime_handler"...

- AdmissionReview objects sent for the creation of Namespace API objects now populate the `namespace` attribute consistently (previously the `namespace` attribute was empty for Namespace creation via POST requests, and populated for Namespace creation via server-side-apply...

* Add support for node side CSI volume expansion ([#74863](https://github.com/kubernetes/kubernetes/pull/74863), [@gnufied](https://github.com/gnufied))
* 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

* Add `Option` field to the admission webhook `AdmissionReview` API that provides the operation options (e.g. `DeleteOption` or `CreateOption`) for the operation being performed. ([#77563](https://github.com/kubernetes/kubernetes/pull/77563), [@jpbetz](https://github.com/jpbetz))

Warnings can also be returned by [admission webhooks](https://kubernetes.io/docs/reference/access-authn-authz/extensible-admission-controllers/#admissionreview-response-warning),
and specified for [deprecated versions of custom resources](https://kubernetes.io/docs/tasks/extend-kubernetes/custom-resources/custom-resource-definition-versioning/#version-deprecation).