- kube-apiserver: a new `--requestheader-uid-headers` flag allows configuring request header authentication to obtain the authenticating user's UID from the specified headers. The suggested value for the new option is `X-Remote-Uid`. When specified, the `kube-system/extension-apiserver-authentication` configmap will include the value in its `.data[requestheader-uid-headers]` field. ([#115834](https://github.com/kubernetes/kubernetes/pull/115834), [@stlaz](...

*   It is now possible to set multiple manifest URL headers with the kubelet's `--manifest-url-header` flag. Multiple headers for the same key will be added in the order provided. The ManifestURLHeader field in KubeletConfiguration object (kubeletconfig/v1alpha1) is now a map[string][]string, which facilitates writing JSON and YAML files....

- Changed: default "Accept-Encoding" header removed from HTTP probes. See https://kubernetes.io/docs/tasks/configure-pod-container/configure-liveness-readiness-startup-probes/#http-probes ([#96127](https://github.com/kubernetes/kubernetes/pull/96127), [@fonsecas72](https://github.com/fonsecas72)) [SIG Network and Node]

- Kube-apiserver: sets an upper-bound on the lifetime of idle keep-alive connections and the time to read the headers of incoming requests. ([#103958](https://github.com/kubernetes/kubernetes/pull/103958), [@liggitt](https://github.com/liggitt))

- Added a path `/header?key=` to `agnhost netexec` allowing one to view what the header value is of the incoming request.

  Ex:
  ```
  $ curl -H "X-Forwarded-For: something" 172.17.0.2:8080/header?key=X-Forwarded-For
  something
  ```

### Other (Cleanup or Flake)

- Kube-apiserver: sets an upper-bound on the lifetime of idle keep-alive connections and time to read the headers of incoming requests ([#103958](https://github.com/kubernetes/kubernetes/pull/103958), [@liggitt](https://github.com/liggitt)) [SIG API Machinery and Node]

## Dependencies

### Added
_Nothing has changed._

* Fixes CVE-2019-11250: client-go header logging (at verbosity levels >= 7) now masks `Authorization` header contents ([#81330](https://github.com/kubernetes/kubernetes/pull/81330), [@tedyu](https://github.com/tedyu))

* The `--insecure-allow-any-token` flag has been removed from the API server. Users of the flag should use impersonation headers instead for debugging. ([#49045](https://github.com/kubernetes/kubernetes/pull/49045), [@ericchiang](https://github.com/ericchiang))

- Kube-apiserver: multiple comma-separated protocols in a single X-Stream-Protocol-Version header are now recognized, in addition to multiple headers, complying with RFC2616 ([#89857](https://github.com/kubernetes/kubernetes/pull/89857), [@tedyu](https://github.com/tedyu)) [SIG API Machinery]

- Fixed a bug that unintentionally overrides custom Accept headers in http (live-/readiness)-probes if the header is in lowercase. ([#114606](https://github.com/kubernetes/kubernetes/pull/114606), [@tuunit](https://github.com/tuunit))