* Add secretbox and AES-CBC encryption modes to at rest encryption.  AES-CBC is considered superior to AES-GCM because it is resistant to nonce-reuse attacks, and secretbox uses Poly1305 and XSalsa20. ([#46916](https://github.com/kubernetes/kubernetes/pull/46916), [@smarterclayton](https://github.com/smarterclayton))

- Fixed a regression in kube-proxy where it might refuse to start if given
  single-stack IPv6 configuration options on a node that has both IPv4 and
  IPv6 IPs. ([#121008](https://github.com/kubernetes/kubernetes/pull/121008), [@danwinship](https://github.com/danwinship)) [SIG Network]

- Add flag --lease-reuse-duration-seconds for kube-apiserver to config etcd lease reuse duration. ([#97009](https://github.com/kubernetes/kubernetes/pull/97009), [@lingsamuel](https://github.com/lingsamuel)) [SIG API Machinery and Scalability]

- A fix in the `resource.k8s.io/v1alpha1/ResourceClaim` API avoids harmless (?) ".status.reservedFor: element 0: associative list without keys has an element that's a map type" errors in the apiserver. Validation now rejects the incorrect reuse of the same UID in different entries. ([#115354](https://github.com/kubernetes/kubernetes/pull/115354), [@pohly](https://github.com/pohly))

    * action required: Cloud providers other than GCE might want to update their deployments or sample yaml files to reuse the role created via add-on.

### Other notable changes

    * action required: Cloud providers other than GCE might want to update their deployments or sample yaml files to reuse the role created via add-on.

### Other notable changes

- IPVS proxier now set net/ipv4/vs/conn_reuse_mode to 0 by default, which will highly improve IPVS proxier performance. ([#71114](https://github.com/kubernetes/kubernetes/pull/71114), [@Lion-Wei](https://github.com/Lion-Wei))

* A cluster-autoscaler ClusterRole is added to cover only the functionality required by Cluster Autoscaler and avoid abusing system:cluster-admin role. Cloud providers other than GCE might want to update their deployments or sample yaml files to reuse the role created via add-on. ([#64503](https://github.com/kubernetes/kubernetes/pull/64503), [@kgolab](https://github.com/kgolab))

### SIG Azure

  * Add secretbox and AES-CBC encryption modes to at rest encryption. AES-CBC is considered superior to AES-GCM because it is resistant to nonce-reuse attacks, and secretbox uses Poly1305 and XSalsa20. ([#46916](https://github.com/kubernetes/kubernetes/pull/46916), [@smarterclayton](https://github.com/smarterclayton))

* Bug fixes:

   ([#122276](https://github.com/kubernetes/kubernetes/pull/122276), [@pohly](https://github.com/pohly))
- Added a CBOR implementation of `runtime.Serializer`. Until CBOR graduates to Alpha, API servers will refuse to start if configured with CBOR support. ([#122881](https://github.com/kubernetes/kubernetes/pull/122881), [@benluddy](https://github.com/benluddy))
- Added a alpha feature, behind the `RelaxedEnvironmentVariableValidation` feature gate.