- Kubeadm: added the ControlPlaneKubeletLocalMode feature gate. It can be used to tell kubeadm to use the local kube-apiserver endpoint for the kubelet when creating a cluster with "kubeadm init" or when joining control plane nodes with "kubeadm join".  The "kubeadm join" workflow now includes two new experimental phases called "con...

It upgrades the version of Starlette to `0.15.0`, now based on [AnyIO](https://anyio.readthedocs.io/en/stable/), and the internal async components in **FastAPI** are now based on AnyIO as well, making it compatible with both **asyncio** and **Trio**.

You can read the docs about running [FastAPI with Trio using Hypercorn](https://fastapi.tiangolo.com/deployment/manually/#hypercorn-with-trio).

- The apiserver debug endpoint `/debug/api_priority_and_fairness/dump_requests` has been extended to dump executing requests as well as queued ones.  A column for StartTime has been added to the returned table, with the queued requests having a StartTime of "0001-01-01T00:00:00Z".  The executing requests have a RequestIndexInQueue of -1, and the QueueIndex is also -1 for priority...

                                type: string
                              metric:
                                description: |-
                                  One of the well-known [Istio Standard Metrics](https://istio.io/latest/docs/reference/config/metrics/).

- 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))

- 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

Subject to the terms and conditions of this License, each Contributor hereby grants to You a perpetual, worldwide, non-exclusive, no-charge, royalty-free, irrevocable (except as stated in this section) patent license to make, have made, use, offer to sell, sell, import, and otherwise transfer the Work, where such license applies only to those patent claims licensable by such Contributor that are necessarily infringed by their Contribution(s) alone or by combination of their Contribution(s) with the Work...

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.