- Added `client-go` support for upgrading subresource fields from client-side to server-side management. ([#123484](https://github.com/kubernetes/kubernetes/pull/123484), [@erikgb](https://github.com/erikgb))
- Added `exec-interactive-mode` and `exec-provide-cluster-info` flags in kubectl config set-credentials command. ([#122023](https://github.com/kubernetes/kubernetes/pull/122023), [@ardaguclu](https://github.com/ardaguclu))

* Fix for Pod stuck in ContainerCreating with error "Volume is not yet attached according to node". ([#50806](https://github.com/kubernetes/kubernetes/pull/50806), [@verult](https://github.com/verult))
* Fix initial exec terminal dimensions. ([#51126](https://github.com/kubernetes/kubernetes/pull/51126), [@chen-anders](https://github.com/chen-anders))

	// in a 16 disk Erasure setup. The original disks are 'replaced' with
	// naughtyDisks that fail after 'f' successful StorageAPI method
	// invocations, where f - [0,2)
	for f := range 2 {
		t.Run("exec-"+strconv.Itoa(f), func(t *testing.T) {
			diskErrors := make(map[int]error)
			for i := 0; i <= f; i++ {
				diskErrors[i] = nil
			}
			erasureDisks := xl.getDisks()
			for i := range erasureDisks[:9] {

or GA.
  * New Flex Volume Plugin enables users to use out-of-process volume plugins that
are installed to “/usr/libexec/kubernetes/kubelet-plugins/volume/exec/” on
every node, instead of being compiled into the Kubernetes binary. See [example](examples/volumes/flexvolume/README.md) for details.
  * vendor volumes into a pod. It expects vendor drivers are installed in the

* Fixed regression in initial kubectl exec terminal dimensions ([#51127](https://github.com/kubernetes/kubernetes/pull/51127), [@chen-anders](https://github.com/chen-anders))

This release also contains a number of bug fixes to the feature set. Aspiring plugin authors can look at [sample-exec-plugin](https://github.com/ankeesler/sample-exec-plugin) as a way to get started.

### Bug or Regression

- Fix an ephemeral port exhaustion bug caused by improper connection management that occurred when a large number of objects were handled by kubectl while exec auth was in use. ([#112337](https://github.com/kubernetes/kubernetes/pull/112337), [@enj](https://github.com/enj)) [SIG API Machinery and Auth]

### Other (Cleanup or Flake)

- "Removed the ability to run `kubectl exec [POD] [COMMAND]` without a `--` separator.
  The `--` separator has been recommended since the Kubernetes v1.18 release, which also deprecated the legacy way of invoking `kubectl exec`.
  

## Urgent Upgrade Notes 

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

kubernetes/kubernetes/pull/58973), [@verb](https://github.com/verb))

* The default Flexvolume plugin directory for COS images on GCE has changed to `/home/kubernetes/flexvolume`, rather than `/etc/srv/kubernetes/kubelet-plugins/volume/exec`. Existing Flexvolume installations in clusters using COS images must be moved to the new directory, and installation processes must be updated with the new path. ([#58171](https://github.com/kubernetes/kubernetes/pull/58171), [@verult](https://github.com/verult))...