- https://github.com/kubernetes-sigs/kustomize/issues/4731: Remove a potential build-time side-effect in ConfigMapGenerator and SecretGenerator, which loaded values from the local environment under some circumstances, breaking kustomize build's side-effect-free promise. While this behavior was never intended, we deprecated it and are announcing it as a breaking change since it existed for a long time. See also the Eschewed...

  * Note that because any taints you might have created with Kubernetes 1.5 can only affect the scheduling of new pods (the `NoExecute` taint effect is introduced in 1.6), neither the master upgrade nor your running `kubectl taint` to re-create the taints will affect pods that are already running.

- Controller-manager: the following flags have no effect and would be removed in v1.24:
  - `--port`
  - `--address`
  The insecure port flags `--port` may only be set to 0 now.
- Kube-scheduler: the `--port` and `--address` flags have no effect and would be removed in v1.24.
  The insecure port flags `--port` may only be set to 0 now.

- hyperkube: Use debian-hyperkube-base@v1.1.0 image
  
    A previous release built hyperkube using the debian-hyperkube-base@v1.0.0,
    which was updated to address a CVE in the CNI plugins.
    
    A side-effect of using this new image was that the networking packages
    (namely `iptables`) drifted from the versions used in the kube-proxy images.
  
    The following issues were filed on kube-proxy failures when using hyperkube:

- Graduated pod scheduling gates to general availability.
  The `PodSchedulingReadiness` feature gate no longer has any effect, and the
  `.spec.schedulingGates` field is always available within the Pod and PodTemplate APIs. ([#123575](https://github.com/kubernetes/kubernetes/pull/123575), [@Huang-Wei](https://github.com/Huang-Wei))

* Webhooks now do not skip cluster-scoped resources. Before upgrading your Kubernetes clusters, double check whether you have configured webhooks for cluster-scoped objects (e.g., nodes, persistentVolume), as these webhooks will start to take effect. Delete/modify the configs if that's not desirable. ([#58185](https://github.com/kubernetes/kubernetes/pull/58185), [@caesarxuchao](https://github.com/caesarxuchao))

 
## Changes by Kind

### Deprecation

- Controller-manager: the following flags have no effect and would be removed in v1.24:
  - `--port`
  - `--address`
  The insecure port flags `--port` may only be set to 0 now.
  
  In addtion, please be careful that:

- The kube-apiserver ability to serve on an insecure port, deprecated since v1.10, has been removed. The insecure address flags `--address` and `--insecure-bind-address` have no effect in kube-apiserver and will be removed in v1.24. The insecure port flags `--port` and `--insecure-port` may only be set to 0 and will be removed in v1.24. ([#95856](https://github.com/kubernetes/kubernetes/pull/95856), [@knight42](https://github.com/knight42),...

### Scheduling

- Tolerations with the same key and effect will be merged into one that has the value of the latest toleration for best effort pods. ([#75985](https://github.com/kubernetes/kubernetes/pull/75985), [@ravisantoshgudimetla](https://github.com/ravisantoshgudimetla))

type is not the same as an initialized but empty value of the same type.
Consequently, taking the address of an empty slice or map composite literal
does not have the same effect as allocating a new slice or map value with
<a href="#Allocation">new</a>.
</p>

<pre>
p1 := &amp;[]int{}    // p1 points to an initialized, empty slice with value []int{} and length 0