* `v1beta1` RoleBinding/ClusterRoleBinding subjects changed `apiVersion` to `apiGroup` to fully-qualify a subject. ServiceAccount subjects default to an apiGroup of `""`, User and Group subjects default to an apiGroup of `"rbac.authorization.k8s.io"`. ([#41184](https://github.com/kubernetes/kubernetes/pull/41184), [@liggitt](https://github.com/liggitt))

### Action Required

* `kubectl create rolebinding` and `kubectl create clusterrolebinding` no longer allow specifying multiple subjects as comma-separated arguments. Use repeated `--user`, `--group`, or `--serviceaccount` arguments to specify multiple subjects.  ([#43903](https://github.com/kubernetes/kubernetes/pull/43903), [@xilabao](https://github.com/xilabao))

### Other notable changes

* Update to go1.10.8 ([#73329](https://github.com/kubernetes/kubernetes/pull/73329), [@ixdy](https://github.com/ixdy))
* Allow for watching objects larger than 1MB given etcd accepts objects of size up to 1.5MB ([#72053](https://github.com/kubernetes/kubernetes/pull/72053), [@wojtek-t](https://github.com/wojtek-t))

* RBAC objects are now stored in etcd in v1 format. After completing an upgrade to 1.9, RBAC objects (Roles, RoleBindings, ClusterRoles, ClusterRoleBindings) should be migrated...

* The `--remove-extra-subjects` and `--remove-extra-permissions` flags have been enabled for `kubectl auth reconcile` ([#64541](https://github.com/kubernetes/kubernetes/pull/64541), [@mrogers950](https://github.com/mrogers950))

  `delete`, `describe`, `edit`, `get`, `label,` and `set`. `--include-uninitialized=true` makes
  kubectl commands apply to uninitialized objects, which by default are ignored
  if the names of the objects are not provided. `--all` also makes kubectl
  commands apply to uninitialized objects. See the
  [initializer documentation](https://kubernetes.io/docs/admin/extensible-admission-controllers/) for more details.

#### Other API changes:

- Fixed a performance issue applying json patches to deeply nested objects ([#93812](https://github.com/kubernetes/kubernetes/pull/93812), [@liggitt](https://github.com/liggitt)) [SIG API Machinery, CLI, Cloud Provider, Cluster Lifecycle and Instrumentation]

* The `spec.SecurityContext.Sysctls` field is now dropped during creation of `Pod` objects unless the `Sysctls` feature gate is enabled. ([#72752](https://github.com/kubernetes/kubernetes/pull/72752), [@rajathagasthya](https://github.com/rajathagasthya))
    * The `spec.AllowedUnsafeSysctls` and `spec.ForbiddenSysctls` fields are now dropped during creation of `PodSecurityPolicy` objects unless the `Sysctls` feature gate is enabled.

l/59298), [@jpbetz](https://github.com/jpbetz))

* The `meta.k8s.io/v1alpha1` objects for retrieving tabular responses from the server (`Table`) or fetching just the `ObjectMeta` for an object (as `PartialObjectMetadata`) are now beta as part of `meta.k8s.io/v1beta1` and configurations must be changed to use the new API.  Clients may request alternate representations of normal Kubernetes objects by passing an `Accept` header like `application/json;as=Table;g=meta.k8s.io;v=v1beta1` or...