- Ceph RBD volume plugin now does not use any keyring (`/etc/ceph/ceph.client.lvs01cinder.keyring`, `/etc/ceph/ceph.keyring`, `/etc/ceph/keyring`, `/etc/ceph/keyring.bin`) for authentication. Ceph user credentials must be provided in PersistentVolume objects and referred Secrets. ([#75588](https://github.com/kubernetes/kubernetes/pull/75588), [@smileusd]...

- Secure serving on port 10258 to cloud-controller-manager (configurable via `--secure-port`) is now enabled. Delegated authentication and authorization are to be configured using the same flags as for aggregated API servers. Without configuration, the secure port...

- Kubeadm: add the deprecated flag --port=0 to kube-controller-manager and kube-scheduler manifests to disable insecure serving. Without this flag the components by default serve (e.g. /metrics) insecurely on the default node interface (controlled by --address). Users that wish to override this behavior and enable insecure serving can pass a custom --port=X via kubeadm's "extraArgs" mechanic for these components. ([#92720](https://github.com/kubernetes/kubernetes/pull/92720),...

- Kube-apiserver: fixes a 1.27+ regression in watch stability by serving watch requests without a resourceVersion from the watch cache by default, as in <1.27 (disabling the change in #115096 by default). This mitigates the impact of an etcd watch bug (https://github.com/etcd-io/etcd/pull/17555). If the 1.27 change in...

        * requests from a node for a TLS serving certificate for itself are approved if the CSR creator has `create` permission on the `certificatesigningrequests` resource and the `selfnodeserver` subresource in the `certificates.k8s.io` API group

([#57902](https://github.com/kubernetes/kubernetes/pull/57902), [@kawych](https://github.com/kawych))

* On cluster provision or upgrade, kubeadm now generates certs and secures all connections to the etcd static-pod with mTLS. This includes the etcd serving cert, the etcd peer cert, and the apiserver etcd client cert. Flags and hostMounts are added to the etcd and apiserver static-pods to load these certs. For connections to etcd, https is now used in favor of http. ([#57415](https://github.com/kube...

- Kube-apiserver: fixes a 1.27+ regression in watch stability by serving watch requests without a resourceVersion from the watch cache by default, as in <1.27 (disabling the change in #115096 by default). This mitigates the impact of an etcd watch bug (https://github.com/etcd-io/etcd/pull/17555). If the 1.27 change in...

## Changelog since v1.21.8

## Changes by Kind

### Feature

- kube-controller-manager and cloud-controller-manager now hold generated serving certificates in-memory unless a writeable location is specified with --cert-dir ([#69884](https://github.com/kubernetes/kubernetes/pull/69884), [@liggitt](https://github.com/liggitt))

Node.  There is an open PR ([#48189](https://github.com/kubernetes/kubernetes/pull/48189)) to resolve this issue, but as this issue also exists in 1.6, and as we do not wish to risk release stability by merging it directly prior to a release without sufficient testing, we have decided to defer merging the PR until the next point release for each minor version ([#48190](https://github.com/kubernetes/kubernetes/pull/48190)).

* Protobuf serialization does not distinguish between `[]` and `null`....