- Improvements were made to `kubeadm reset` related to cleaning  etcd and notifying the user about the state of iptables.
- kubeadm commands now print warnings if input YAML documents contain unknown or duplicate fields.
- kubeadm now properly recognizes Docker 18.09.0 and newer, but still treats 18.06 as the default supported version.

* set config.BindAddress to IPv4 address "127.0.0.1" if not specified ([#83822](https://github.com/kubernetes/kubernetes/pull/83822), [@zouyee](https://github.com/zouyee))

  - `spec.usages` is now required, may not contain duplicate values, and must only contain known usages
  - `status.conditions` may not contain duplicate types
  - `status.conditions[*].status` is now required

- CRD deep copies should no longer contain shallow copies of `JSONSchemaProps.XValidations`. ([#107956](https://github.com/kubernetes/kubernetes/pull/107956), [@benluddy](https://github.com/benluddy))

- Kube-apiserver: removed apf_fd from server logs (added in 1.23.0) which could contain data identifying the requesting user ([#108634](https://github.com/kubernetes/kubernetes/pull/108634), [@jupblb](https://github.com/jupblb)) [SIG API Machinery and Scalability]

## Dependencies

### Added

- Server Side Apply now treats all <Some>Selector fields as atomic (meaning the entire selector is managed by a single writer and updated together), since they contain interrelated and inseparable fields that do not merge in intuitive ways. ([#97989](https://github.com/kubernetes/kubernetes/pull/97989), [@Danil-Grigorev](https://github.com/Danil-Grigorev)) [SIG API Machinery]

- Server Side Apply now treats LabelSelector fields as atomic (meaning the entire selector is managed by a single writer and updated together), since they contain interrelated and inseparable fields that do not merge in intuitive ways. ([#93901](https://github.com/kubernetes/kubernetes/pull/93901), [@jpbetz](https://github.com/jpbetz)) [SIG API Machinery, Auth, CLI, Cloud Provider, Cluster Lifecycle, Instrumentation,...

### Other (Cleanup or Flake)

- When retrieving event resources, the reportingController and reportingInstance fields in the event will contain values. ([#120065](https://github.com/kubernetes/kubernetes/pull/120065), [@HirazawaUi](https://github.com/HirazawaUi)) [SIG Instrumentation]

## Dependencies

### Added
_Nothing has changed._

### Changed

## Changelog since v1.15.6

### Other notable changes

* Allow Secret & ConfigMap keys to contain caps, dots, and underscores ([#25458](https://github.com/kubernetes/kubernetes/pull/25458), [@errm](https://github.com/errm))