* Use authorization to limit users' ability to use specific PodSecurityPolicy objects

**What is the impact?**

A user that is authorized to create pods can make use of any existing PodSecurityPolicy, even ones they are not authorized to use.

**How can I mitigate this prior to installing 1.5.5?**

1. Export existing PodSecurityPolicy objects:
  * `kubectl get podsecuritypolicies -o yaml > psp.yaml`

- Introduced a feature gate mechanism to `client-go`. Depending on the actual implementation, users can control features via environmental variables or command line options. ([#122555](https://github.com/kubernetes/kubernetes/pull/122555), [@p0lyn0mial](https://github.com/p0lyn0mial))

* Provide kubernetes-controller-manager flags to control volume attach/detach reconciler sync.  The duration of the syncs can be controlled, and the syncs can be shut off as well.  ([#39551](https://github.com/kubernetes/kubernetes/pull/39551), [@chrislovecnm](https://github.com/chrislovecnm))