* Pod spec is mutable when the pod is uninitialized. The API server requires the pod spec to be valid even if it's uninitialized. Updating the status field of uninitialized pods is invalid.([#51733](https://github.com/kubernetes/kubernetes/pull/51733))

* Action required: validation rule on metadata.initializers.pending[x].name is tightened. The initializer name needs to contain at least three segments separated by dots. If you create objects with pending initializers, (i.e., not relying on apiserver adding pending initializers according to initializerconfiguration), you need to update the initializer name in existing objects and in configuration files to comply to the new validation rule. ([#512...

- Fixed incorrect watch events when a watch is initialized simultanously with a reinitializing watchcache. ([#116436](https://github.com/kubernetes/kubernetes/pull/116436), [@wojtek-t](https://github.com/wojtek-t))

- The alpha `Initializers` admission plugin is no longer enabled by default. This matches the off-by-default behavior of the alpha API which drives initializer behavior. ([#66039](https://github.com/kubernetes/kubernetes/pull/66039), [@liggitt](https://github.com/liggitt))

Kubernetes with a different admission-control flag on API server. ([#58080](https://github.com/kubernetes/kubernetes/pull/58080), [@simonferquel](https://github.com/simonferquel))

* Alpha Initializers have been removed from kubeadm admission control.  Kubeadm users who still want to use Initializers can use apiServerExtraArgs through the kubeadm config file to enable it when booting up the cluster. ([#58428](https://github.com/kubernetes/kubernetes/pull/58428), [@dixudx](https://github.com/dixudx))...

## Changelog since v1.17.0-beta.2

### Other notable changes

* kubeadm: fix a panic in case the KubeProxyConfiguration feature gates were not initialized. ([#85524](https://github.com/kubernetes/kubernetes/pull/85524), [@Arvinderpal](https://github.com/Arvinderpal))

## Changelog since v1.18.2

## Changes by Kind

### Bug or Regression
 - An issue preventing GCP cloud-controller-manager running out-of-cluster to initialize new Nodes is now fixed. ([#90057](https://github.com/kubernetes/kubernetes/pull/90057), [@ialidzhikov](https://github.com/ialidzhikov)) [SIG Apps and Cloud Provider]

    * This more closely aligns rest client as a generic RESTful client, while preserving the special Kube API extended error handling for the `Get` and `Into` methods (which most Kube clients use).
* Making the pod.alpha.kubernetes.io/initialized annotation optional in PetSet pods ([#35739](https://github.com/kubernetes/kubernetes/pull/35739), [@foxish](https://github.com/foxish))

- For scheduler plugin developers: the scheduler framework's shared PodInformer is now initialized with empty indexers. This enables scheduler plugins to add their extra indexers. Note that only non-conflict indexers are allowed to be added. ([#110663](https://github.com/kubernetes/kubernetes/pull/110663), [@fromanirh](https://github.com/fromanirh))...

- Fixed bug where a nonzero exit code was returned when initializing zsh completion even though zsh completion was successfully initialized ([#88165](https://github.com/kubernetes/kubernetes/pull/88165), [@brianpursley](https://github.com/brianpursley)) [SIG CLI]