* The OpenID Connect authenticator can now use a custom prefix, or omit the default prefix, for username and groups claims through the --oidc-username-prefix and --oidc-groups-prefix flags. For example, the authenticator can map a user with the username "jane" to "google:jane" by supplying the "google:" username prefix. ([#50875](https://github.com/kubernetes/kubernetes/pull/50875), [@ericchiang](https://github.com/ericchiang))

* The OpenID Connect authenticator can now use a custom prefix, or omit the default prefix, for username and groups claims through the --oidc-username-prefix and --oidc-groups-prefix flags. For example, the authenticator can map a user with the username "jane" to "google:jane" by supplying the "google:" username prefix. ([#50875](https://github.com/kubernetes/kubernetes/pull/50875), [@ericchiang](https://github.com/ericchiang))

## Changelog since v1.13.4

### Other notable changes

* Restores --username and --password flags to kubectl ([#75451](https://github.com/kubernetes/kubernetes/pull/75451), [@liggitt](https://github.com/liggitt))

- When configuring a JWT authenticator:
  
  If `username.expression` used 'claims.email', then 'claims.email_verified' must have been used in `username.expression` or `extra[*].valueExpression` or `claimValidationRules[*].expression`. An example claim validation rule expression that matches the validation automatically applied when `username.claim` is set to 'email' is 'claims.?email_verified.orValue(true)'.

- Use checksums instead of fsyncs to ensure discovery cache integrity ([#110851](https://github.com/kubernetes/kubernetes/pull/110851), [@negz](https://github.com/negz)) [SIG API Machinery]
- UserName check for 'ContainerAdministrator' is now case-insensitive if runAsNonRoot is set to true on Windows. ([#111009](https://github.com/kubernetes/kubernetes/pull/111009), [@marosset](https://github.com/marosset))

- UserName check for 'ContainerAdministrator' is now case-insensitive if runAsNonRoot is set to true on Windows. ([#112212](https://github.com/kubernetes/kubernetes/pull/112212), [@PushkarJ](https://github.com/PushkarJ)) [SIG Node, Testing and Windows]

- UserName check for 'ContainerAdministrator' is now case-insensitive if runAsNonRoot is set to true on Windows. ([#112213](https://github.com/kubernetes/kubernetes/pull/112213), [@PushkarJ](https://github.com/PushkarJ)) [SIG Node, Testing and Windows]

- UserName check for 'ContainerAdministrator' is now case-insensitive if runAsNonRoot is set to true on Windows. ([#112211](https://github.com/kubernetes/kubernetes/pull/112211), [@PushkarJ](https://github.com/PushkarJ)) [SIG Node, Testing and Windows]

        * Nodes must use client credentials that place them in the `system:nodes` group with a username of `system:node:<nodeName>` in order to be authorized by the node authorizer (the credentials obtained by the kubelet via TLS bootstrapping satisfy these requirements)

### Other notable changes

* Restores --username and --password flags to kubectl ([#75451](https://github.com/kubernetes/kubernetes/pull/75451), [@liggitt](https://github.com/liggitt))