* API server authentication now caches successful bearer token authentication results for a few seconds. ([#50258](https://github.com/kubernetes/kubernetes/pull/50258), [@liggitt](https://github.com/liggitt))

* kube-apiserver: OIDC authentication now supports requiring specific claims with `--oidc-required-claim=<claim>=<value>` Previously, there was no mechanism for a user to specify claims in the OIDC authentication process that were requid to be present in the ID Token with an expected value. This version now makes it possible to require claims support for the OIDC authentication. It allows users to pass in a `--oidc-required-claims` flag, and `key=value`...

- Kubectl azure authentication: fixed a regression in 1.18.0 where "spn:" prefix was unexpectedly added to the `apiserver-id` configuration in the kubeconfig file ([#89706](https://github.com/kubernetes/kubernetes/pull/89706), [@weinong](https://github.com/weinong)) [SIG API...

 *  New: `EventListener.followUpDecision()` is called each time a response is received. It notifies
    your listener if OkHttp has decided to make a follow-up request. Some common follow-ups are
    authentication challenges and redirects.

 *  New: Handy constants for `Headers.EMPTY`, `RequestBody.EMPTY`, and `ResponseBody.EMPTY`.

 *  New: OkHttp now calls `StrictMode.noteSlowCall()` when initializing TLS on Android. Use

Node API object](https://kubernetes.io/docs/reference/access-authn-authz/admission-controllers/#noderestriction). In authentication, we added alpha-level support for automounting improved service account tokens through projected volumes. We also enabled [audience validation in TokenReview](https://kubernetes.io/docs/reference/generated/kubernetes-api/v1.13/#tokenreview-v1-authentication-k8s-io) for the new tokens for improved scoping. Under audit logging, the new alpha-level "dynamic audit configuration"...

- `system:kube-controller-manager` and `system:kube-scheduler` users are now permitted to perform delegated authentication/authorization checks by default RBAC policy ([#72491](https://github.com/kubernetes/kubernetes/pull/72491), [@liggitt](https://github.com/liggitt))

- github.com/hashicorp/go-syslog: [v1.0.0](https://github.com/hashicorp/go-syslog/tree/v1.0.0)
- github.com/jimstudt/http-authentication: [3eca13d](https://github.com/jimstudt/http-authentication/tree/3eca13d)
- github.com/kisielk/errcheck: [v1.2.0](https://github.com/kisielk/errcheck/tree/v1.2.0)
- github.com/kisielk/gotool: [v1.0.0](https://github.com/kisielk/gotool/tree/v1.0.0)

* client-go: alpha support for out-of-tree exec-based credential providers. For example, a cloud provider could create their own authentication system rather than using the standard authentication provided with Kubernetes. ([#59495](https://github.com/kubernetes/kubernetes/pull/59495), [@ericchiang](https://github.com/ericchiang))

 * no mechanism to differentiate empty from absent. Neither of these components are popular in
 * practice. Typically HTTP applications use other mechanisms for user identification and
 * authentication.
 *
 * ### Host
 *
 * The host identifies the webserver that serves the URL's resource. It is either a hostname like
 * `square.com` or `localhost`, an IPv4 address like `192.168.0.1`, or an IPv6 address like `::1`.

- Kube-up now includes CoreDNS version v1.9.3. ([#110488](https://github.com/kubernetes/kubernetes/pull/110488), [@mzaian](https://github.com/mzaian))
- Kubeadm: Added support for additional authentication strategies in `kubeadm join` with discovery/kubeconfig file: client-go authentication plugins (`exec`), `tokenFile`, and `authProvider.` ([#110553](https://github.com/kubernetes/kubernetes/pull/110553), [@tallaxes](https://github.com/tallaxes))