* kube-apiserver: the experimental in-tree Keystone password authenticator has been removed in favor of extensions that enable use of Keystone tokens. ([#59492](https://github.com/kubernetes/kubernetes/pull/59492), [@dims](https://github.com/dims))

* In-tree support for openstack credentials is now deprecated. please use the "client-keystone-auth" from the cloud-provider-openstack repository. details on how to use this new capability is documented [here](https://github.com/kubernetes/cloud-provider-openstack/blob/master/docs/using-client-keystone-auth.md) ([#64346](https://github.com/kubernetes/kubernetes/pull/64346), [@dims](https://github.com/dims))

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

* Update busybox image link to gcr.io for kube-proxy. ([#53818](https://github.com/kubernetes/kubernetes/pull/53818), [@MrHohn](https://github.com/MrHohn))
* Restores the ability to apply network policy objects against the networking.k8s.io/v1 API ([#54106](https://github.com/kubernetes/kubernetes/pull/54106), [@liggitt](https://github.com/liggitt))

* kube-scheduler: restores ability to run without authentication configuration lookup permissions ([#71755](https://github.com/kubernetes/kubernetes/pull/71755), [@liggitt](https://github.com/liggitt))

### Other notable changes

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

- Restores priority of static control plane pods in the cluster/gce/manifests control-plane manifests ([#89970](https://github.com/kubernetes/kubernetes/pull/89970), [@liggitt](https://github.com/liggitt)) [SIG Cluster Lifecycle and Node]

* kube-scheduler: restores default leader election behavior. leader-elect command line parameter should "true" ([#60524](https://github.com/kubernetes/kubernetes/pull/60524), [@dims](https://github.com/dims))

- Restores priority of static control plane pods in the cluster/gce/manifests control-plane manifests ([#89970](https://github.com/kubernetes/kubernetes/pull/89970), [@liggitt](https://github.com/liggitt)) [SIG Cluster Lifecycle and Node]

## Changelog since v1.15.3

### Other notable changes

* Restores compatibility with kubectl client-side validation when structural schemas are present in a CRD which sets spec.preserveUnknownFields=true ([#82666](https://github.com/kubernetes/kubernetes/pull/82666), [@liggitt](https://github.com/liggitt))