### API Change

- '`kube-apiserver`: adds `--authentication-config` flag for reading `AuthenticationConfiguration`
  files. `--authentication-config` flag is mutually exclusive with the existing `--oidc-*`

- Introduces extension point for external feedback on pod readiness.
kubernetes/kubernetes: [#74434](http://github.com/kubernetes/kubernetes/pull/74434),
kubernetes/enhancements: [#580](https://github.com/kubernetes/enhancements/issues/580) [[kep](https://github.com/kubernetes/enhancements/blob/master/keps/sig-network/580-pod-readiness-gates/README.md)]

Kubeadm: Automate certificate copy between control planes in HA setups

- Remove prometheus cluster monitoring addon from kube-up ([#83442](https://github.com/kubernetes/kubernetes/pull/83442), [@serathius](https://github.com/serathius))
- SourcesReady provides the readiness of kubelet configuration sources such as apiserver update readiness. ([#81344](https://github.com/kubernetes/kubernetes/pull/81344), [@zouyee](https://github.com/zouyee))

- Since golang 1.17 both net.ParseIP and net.ParseCIDR rejects leading zeros in the dot-decimal notation of IPv4 addresses,
  Kubernetes will keep allowing leading zeros on IPv4 address to not break the compatibility.
  IMPORTANT: Kubernetes interprets leading zeros on IPv4 addresses as decimal, users must not rely on parser alignment to not being impacted by the associated security advisory:

- Fixed file permission issues that happened during update of `Secret`/`ConfigMap`/`projected volume` when `fsGroup` is used. The problem caused a race condition where application gets intermittent permission denied error when reading files that were just updated, before the correct permissions were applied. ([#114464](https://github.com/kubernetes/kubernetes/pull/114464), [@tsaarni](https://github.com/tsaarni))

- Check for newer resize fields when deciding recovery feature's status in kubelet ([#131437](https://github.com/kubernetes/kubernetes/pull/131437), [@gnufied](https://github.com/gnufied)) [SIG Storage]
- Disable reading of disk geometry before calling expansion for ext and xfs filesystems ([#131636](https://github.com/kubernetes/kubernetes/pull/131636), [@gnufied](https://github.com/gnufied)) [SIG Storage]

- The underlying format of the `CPUManager` state file has changed. Upgrades should be seamless, but any third-party tools that rely on reading the previous format need to be updated. ([#84462](https://github.com/kubernetes/kubernetes/pull/84462), [@klueska](https://github.com/klueska)) [SIG Node and Testing]

- Kube-apiserver: Each unique set of etcd server overrides specified with `--etcd-servers-overrides` surfaced health checks named `etcd-override-<index>` and `etcd-override-readiness-<index>`. These checks were still excluded by the `?exclude=etcd` and `?exclude=etcd-readiness` directives. ([#129438](https://github.com/kubernetes/kubernetes/pull/129438), [@pacoxu](https://github.com/pacoxu)) [SIG API Machinery and Testing]

- kubeadm: switched the kube-scheduler static Pod to use the endpoints `/livez` (for startup and liveness probes) and `/readyz` (for the readiness probe). Previously, `/healthz` was used for all probes, which is deprecated behavior in the scope of this component. ([#126945](https://github.com/kubernetes/kubernetes/pull/126945), [@liangyuanpeng](https://github.com/liangyuanpeng)) [SIG Cluster...

- Pods will now post their readiness during termination. ([#110418](https://github.com/kubernetes/kubernetes/pull/110418), [@aojea](https://github.com/aojea)) [SIG Network, Node and Testing]