A security issue was discovered in kube-apiserver that could allow an attacker controlled aggregated API server to redirect client traffic to any URL.  This could lead to the client performing unexpected actions as well as leaking the client's credentials to third parties. 

* Exec and portforward actions over SPDY now properly handle redirects sent by the Kubelet ([#44451](https://github.com/kubernetes/kubernetes/pull/44451), [@ncdc](https://github.com/ncdc))

* [beta] SelfSubjectRulesReview, an API that lets a user see what actions they can perform with a namespace, has been added to the authorization.k8s.io API group. This bulk query is intended to enable UIs to show/hide actions based on the end user, and for users to quickly reason about their own permissions.

 ([#64792](https://github.com/kubernetes/kubernetes/pull/64792), [@luxas](https://github.com/luxas))...

  Added `validationActions` to `ValidatingAdmissionPolicyBinding`, enabling validation failures to be handled by any combination of the warn, audit and deny enforcement actions. ([#115973](https://github.com/kubernetes/kubernetes/pull/115973), [@jpbetz](https://github.com/jpbetz))

- kubeadm: increased the verbosity of API client dry-run actions during the subcommands "init", "join", "upgrade" and "reset". It also allowed dry-run on 'kubeadm join' even if there was no existing cluster by utilizing a faked, in-memory cluster-info ConfigMap. ([#126776](https://github.com/kubernetes/kubernetes/pull/126776),...

- Kubeadm: Switched kubeadm to start using the CRI client library instead of shelling out of the `crictl` binary
  for actions against a CRI endpoint. The kubeadm deb/rpm packages will continue to install the `cri-tools`
  package for one more release, but in you must adapt your scripts to install `crictl` manually from

### Auth

- Added `kubectl auth can-i --list` option, which allows users to  know what actions they can do in specific namespaces. ([#64820](https://github.com/kubernetes/kubernetes/pull/64820), [@WanLinghao](https://github.com/WanLinghao))

* The node authorizer now allows nodes to request service account tokens for the service accounts of pods running on them. This allows agents using the node identity to take actions on behalf of local pods. ([#55019](https://github.com/kubernetes/kubernetes/pull/55019), [@mikedanese](https://github.com/mikedanese))

For initial installations, see the [Setup topics](https://kubernetes.io/docs/setup/pick-right-solution/) in the Kubernetes documentation.

To upgrade to this release from a previous version, first take any actions required [Before Upgrading](https://github.com/kubernetes/kubernetes/blob/master/CHANGELOG/CHANGELOG-1.9.md#before-upgrading).