* 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))

- `--log-flush-frequency` had no effect in several commands or was missing. Help and warning texts were not always using the right format for a command (`add_dir_header` instead of `add-dir-header`). Fixing this included cleaning up flag handling in component-base/logs: that package no longer adds flags to the global flag sets. Commands which want the klog and `--log-flush-frequency`...

* Reduce time needed to attach Azure disks ([#40066](https://github.com/kubernetes/kubernetes/pull/40066), [@codablock](https://github.com/codablock))
* Fixes request header authenticator by presenting the request header client CA so that the front proxy will authenticate using its client certificate. ([#40301](https://github.com/kubernetes/kubernetes/pull/40301), [@deads2k](https://github.com/deads2k))

### Other (Cleanup or Flake)

- Client-go header logging (at verbosity levels >= 9) now masks `Authorization` header contents ([#95316](https://github.com/kubernetes/kubernetes/pull/95316), [@sfowl](https://github.com/sfowl)) [SIG API Machinery]

## Dependencies

### Added
_Nothing has changed._

- 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
  ```

- Kube API server accepts `Impersonate-Uid` header to impersonate a user with a specific UID, in the same way that you can currently use `Impersonate-User`, `Impersonate-Group` and `Impersonate-Extra`. ([#99961](https://github.com/kubernetes/kubernetes/pull/99961), [@margocrawf](https://github.com/margocrawf))...

- client-go: The `rest.AnonymousClientConfig(*rest.Config) *rest.Config` helper method no longer copies custom `Transport` and `WrapTransport` fields, because those can be used to inject user credentials. ([#75771](https://github.com/kubernetes/kubernetes/pull/75771), [@liggitt](https://github.com/liggitt))

* Fix issue in converting AWS volume ID from mount paths ([#36840](https://github.com/kubernetes/kubernetes/pull/36840), [@jingxu97](https://github.com/jingxu97))
* Correct env var name in configure-helper ([#33848](https://github.com/kubernetes/kubernetes/pull/33848), [@mtaufen](https://github.com/mtaufen))

- Added `kubectl node drain` helper callbacks `OnPodDeletionOrEvictionStarted`
  and `OnPodDeletionOrEvictionFailed`; people extending `kubectl` can use these
  new callbacks for more granularity. Deprecated the `OnPodDeletedOrEvicted`

* Flush conntrack state for removed/changed UDP Services ([#22573](https://github.com/kubernetes/kubernetes/pull/22573), [@freehan](https://github.com/freehan))
* Allow setting the Host header in a httpGet probe ([#24292](https://github.com/kubernetes/kubernetes/pull/24292), [@errm](https://github.com/errm))