- Added a `kubernetes_feature_enabled` metric which will tell you if a feature is enabled. ([#112652](https://github.com/kubernetes/kubernetes/pull/112652), [@logicalhan](https://github.com/logicalhan))

* Fixes bugs that make apiserver panic when aggregating valid but not well formed OpenAPI spec ([#63635](https://github.com/kubernetes/kubernetes/pull/63635), [@roycaihw](https://github.com/roycaihw))

* Add ipset and udevadm to the hyperkube base image. ([#61357](https://github.com/kubernetes/kubernetes/pull/61357), [@rphillips](https://github.com/rphillips))
* Fixes bugs that make apiserver panic when aggregating valid but not well formed OpenAPI spec ([#63626](https://github.com/kubernetes/kubernetes/pull/63626), [@roycaihw](https://github.com/roycaihw))

- Using `--log-file` is known to be problematic in 1.15. This presents as things being logged multiple times to the same file. The behaviour and details of this issue, as well as some preliminary attempts at fixing it are documented [here](https://github.com/kubernetes/kubernetes/issues/78734#issuecomment-501372131)

## Urgent Upgrade Notes

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.