- `kube-apiserver` added:
  - `alpha` support (guarded by the `ServiceAccountTokenJTI` feature gate) for adding a `jti` (JWT ID) claim to service account tokens it issues, adding an `authentication.kubernetes.io/credential-id` audit annotation in audit logs when the tokens are issued, and `authentication.kubernetes.io/credential-id` entry in the extra user info when the token is used to authenticate.

CSI Service Account Token feature moves to Beta in 1.21. This feature improves the security posture and allows CSI drivers to receive pods' [bound service account tokens](https://github.com/kubernetes/enhancements/blob/master/keps/sig-auth/1205-bound-service-account-tokens/README.md). This feature also provides a knob to re-publish volumes so that short-lived volumes can be refreshed.

### CSI Health Monitoring

* **[alpha]** New Bootstrap Token authentication and management method. Works well with kubeadm. kubeadm now supports managing tokens, including time based expiration, after the cluster is launched.  See [kubeadm reference docs](https://kubernetes.io/docs/admin/kubeadm/#manage-tokens) for details.
* **[alpha]** Adds a new cloud-controller-manager binary that may be used for testing the new out-of-core cloudprovider flow.

* vSphere: Fix attach volume failing on the first try. ([#51217](https://github.com/kubernetes/kubernetes/pull/51217), [@BaluDontu](https://github.com/BaluDontu))
* azure: support retrieving access tokens via managed identity extension ([#48854](https://github.com/kubernetes/kubernetes/pull/48854), [@colemickens](https://github.com/colemickens))

* The node authorizer now allows nodes to request service account tokens for the service accounts of pods running on them. This allows agents using the node identity to take actions on behalf of local pods. ([#55019](https://github.com/kubernetes/kubernetes/pull/55019), [@mikedanese](https://github.com/mikedanese))

  - `--service-account-key-file`, set to one or more files containing one or more public keys used to verify tokens.

- Node information is now embedded into Pod-bound service account tokens as additional metadata. The 'JTI' field is set in issued service account tokens, and this information is embedded as `authentication.kubernetes.io/credential-id` in the user's ExtraInfo. ([#123135](https://github.com/kubernetes/kubernetes/pull/123135), [@munnerz](https://github.com/munnerz))...

-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" adds support for [dynamically registering webhooks...

</p>

<h3 id="Tokens">Tokens</h3>

<p>
Tokens form the vocabulary of the Go language.
There are four classes: <i>identifiers</i>, <i>keywords</i>, <i>operators
and punctuation</i>, and <i>literals</i>.  <i>White space</i>, formed from
spaces (U+0020), horizontal tabs (U+0009),
carriage returns (U+000D), and newlines (U+000A),
is ignored except as it separates tokens

* kubeadm: kubelets in kubeadm clusters now disable the readonly port (10255). If you're relying on unauthenticated access to the readonly port, please switch to using the secure port (10250). Instead, you can now use ServiceAccount tokens when talking to the secure port, which will make it easier to get access to, for example, the `/metrics` endpoint of the kubelet, securely. ([#64187](https://github.com/kubernetes/kubernetes/pull/64187), [@luxas](https://github.com/luxas))