### Feature

- 'kubeadm: enhanced the "patches" functionality to be able to patch coredns
  deployment. The new patch target is called "corednsdeployment" (e.g. patch file
  "corednsdeployment+json.json"). This makes it possible to apply custom patches

- Very large patches may now be specified to `kubectl patch` with the `--patch-file` flag instead of including them directly on the command line. The `--patch` and `--patch-file` flags are mutually exclusive. ([#93548](https://github.com/kubernetes/kubernetes/pull/93548), [@smarterclayton](https://github.com/smarterclayton)) [SIG CLI]

### (No, really, you MUST read this before you upgrade)

- Kubeadm: remove the deprecated flag `--experimental-patches` for the `init|join|upgrade` commands. The flag `--patches` is no longer allowed in a mixture with the flag `--config`. Please use the kubeadm configuration for setting patches for a node using `{Init|Join}Configuration.patches`. ([#104065](https://github.com/kubernetes/kubernetes/pull/104065), [@pacoxu](https://github.com/pacoxu))

  
  - https://github.com/kubernetes-sigs/kustomize/pull/4911: Drop support for a very old, legacy style of patches. patches used to be allowed to be used as an alias for patchesStrategicMerge in kustomize v3. You now have to use patchesStrategicMerge explicitly, or update to the new syntax supported by patches. See examples in the PR description of https://github.com/kubernetes-sigs/kustomize/pull/4911.

- Kubeadm: deprecate the feature `--experimental-kustomize` in favor of `--experimental-patches`. The supported patch formats are the same as "kubectl patch". They are read as files from a directory and can be applied to kubeadm components during init/join/upgrade. Only patching of static Pods is supported for the time being. ([#92017](https://github.com/kubernetes/kubernetes/pull/92017),...

* kube-apiserver: Fixed a regression accepting patch requests > 1MB ([#84963](https://github.com/kubernetes/kubernetes/pull/84963), [@liggitt](https://github.com/liggitt))
* kube-apiserver: fixed a bug that could cause a goroutine leak if the apiserver encountered an encoding error serving a watch to a websocket watcher ([#84693](https://github.com/kubernetes/kubernetes/pull/84693), [@tedyu](https://github.com/tedyu))

In Kubernetes 1.18, there are two significant additions to Ingress: A new `pathType` field and a new `IngressClass` resource. The `pathType` field allows specifying how paths should be matched. In addition to the default `ImplementationSpecific` type, there are new `Exact` and `Prefix` path types. 

- Fix data race in kubelet status manager. ([#136205](https://github.com/kubernetes/kubernetes/pull/136205), [@HirazawaUi](https://github.com/HirazawaUi)) [SIG Node]
- Fix issues where server side apply patches operations incorrectly treat empty arrays and maps as absent.
  Fix issue where client-go's `Extract{TypeName}()` and `Extract{TypeName}From() functions incorrectly treat empty arrays and maps as absent.

* K8s 1.5 keeps container-vm as the default node image on GCE for backwards compatibility reasons. Please beware that container-vm is officially deprecated (supported with security patches only) and you should replace it with GCI if at all possible. You can review the migration guide here for more detail: https://cloud.google.com/container-engine/docs/node-image-migration ([#36822](https://github.com/kubernetes/kubernetes/pull/36822),...

incorrect. If watching objects with a filter, when an update was made that no longer matched the filter a DELETE event was correctly sent. However, the object that was returned by that delete was not the (correct) version before the update, but instead, the newer version. That meant the new object was not matched by the filter. This was a regression from behavior between cached watches on the server side and uncached watches, and thus broke downstream API clients. ([#46223](https://github.com/kubernete...