- `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.

  - This changes the tokens provided to containers at `/var/run/secrets/kubernetes.io/serviceaccount/token` to be time-limited, auto-refreshed, and invalidated when the containing pod is deleted.
  - Clients should reload the token from disk periodically (once per minute is recommended) to ensure they continue to use a valid token. `k8s.io/client-go` version v11.0.0+ and v0.15.0+ reload tokens automatically.

* **[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.

* `--service-account-lookup` now defaults to true, requiring the Secret API object containing the token to exist in order for a service account token to be valid. This enables service account tokens to be revoked by deleting the Secret object containing the token. ([#44071](https://github.com/kubernetes/kubernetes/pull/44071), [@liggitt](https://github.com/liggitt))

    * kube-apiserver: the OpenID Connect authenticator no longer accepts tokens from the Google v3 token APIs, users must switch to the "https://www.googleapis.com/oauth2/v4/token" endpoint.

- If BoundServiceAccountTokenVolume is enabled, cluster admins can use metric `serviceaccount_stale_tokens_total` to monitor workloads that are depending on the extended tokens. If there are no such workloads, turn off extended tokens by starting `kube-apiserver` with flag `--service-account-extend-token-expiration=false` ([#96273](https://github.com/kubernetes/kubernetes/pull/96273), [@zshihang](https://github.com/zshihang)) [SIG API Machinery and Auth]

-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...

- 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))...

</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: The Token-related fields in the `MasterConfiguration` object have now been refactored. Instead of the top-level `.Token`, `.TokenTTL`, `.TokenUsages`, `.TokenGroups` fields, there is now a `BootstrapTokens` slice of `BootstrapToken` objects that support the same features under the `.Token`, `.TTL`, `.Usages`, `.Groups` fields. ([#64408](https://github.com/kubernetes/kubernetes/pull/64408), [@lu...