### Other notable changes

* Kubernetes json deserializer is now case-sensitive to restore compatibility with pre-1.8 servers. ([#65157](https://github.com/kubernetes/kubernetes/pull/65157), [@caesarxuchao](https://github.com/caesarxuchao))
    * If your config files contains fields with wrong case, the config files will be now invalid.

3. Ensure you have added or ran the appropriate tests for your PR: https://git.k8s.io/community/contributors/devel/sig-testing/testing.md
4. If you want *faster* PR reviews, read how: https://git.k8s.io/community/contributors/guide/pull-requests.md#best-practices-for-faster-reviews
5. If the PR is unfinished, see how to mark it: https://git.k8s.io/community/contributors/guide/pull-requests.md#marking-unfinished-pull-requests
-->

for the kubelet in the dropin, a structured configuration file for the kubelet is used, and is expected to be present in `/var/lib/kubelet/config.yaml`. For runtime-detected, instance-specific configuration values, a environment file with dynamically-generated flags at `kubeadm init` or `kubeadm join` run time is used. Finally, if you want to override something specific for the kubelet that can't be done via the kubeadm Configuration file (which is preferred), you might add flags to the `KUBELET_EXTRA_ARGS`...

- Implement `post-filter` extension point for scheduling framework ([#78097](https://github.com/kubernetes/kubernetes/pull/78097), [@draveness](https://github.com/draveness))
- Add Bind extension point of the scheduling framework ([#78513](https://github.com/kubernetes/kubernetes/pull/78513), [@chenchun](https://github.com/chenchun))

- Fixes an issue with the max-in-flight API server filter where the filter could take a long time to process an incoming request if it had been a long time since the last request. ([#96282](https://github.com/kubernetes/kubernetes/pull/96282), [@staebler](https://github.com/staebler)) [SIG API Machinery]

  - `--service-account-key-file`, set to one or more files containing one or more public keys used to verify tokens.

  - `read_vs_write_request_count_watermarks` is removed. ([#110104](https://github.com/kubernetes/kubernetes/pull/110104), [@MikeSpreitzer](https://github.com/MikeSpreitzer)) [SIG API Machinery, Instrumentation...

- Kubeadm: during execution of the "check expiration" command, treat the etcd CA as external if there is a missing etcd CA key file (etcd/ca.key) and perform the proper validation on certificates signed by the...

* Kubernetes server components using `kubeconfig` files no longer default to `http://localhost:8080`.  Administrators must specify a server value in their kubeconfig files. ([#30808](https://github.com/kubernetes/kubernetes/pull/30808), [@smarterclayton](https://github.com/smarterclayton))

## Urgent Upgrade Notes 

### (No, really, you MUST read this before you upgrade)