*   It is now possible to set multiple manifest URL headers with the kubelet's `--manifest-url-header` flag. Multiple headers for the same key will be added in the order provided. The ManifestURLHeader field in KubeletConfiguration object (kubeletconfig/v1alpha1) is now a map[string][]string, which facilitates writing JSON...

* Laid the groundwork for OIDC distributed claims handling in the apiserver authentication token checker. A distributed claim allows the OIDC provider to delegate a claim to a separate URL. ([ref](http://openid.net/specs/openid-connect-core-1_0.html#AggregatedDistributedClaims)). ([#63213](https://github.com/kubernetes/kubernetes/pull/63213), [@filmil](https://github.com/filmil))

  - https://github.com/kubernetes-sigs/kustomize/pull/4985: If you previously included .git in an AWS or Azure URL, we will no longer automatically remove that suffix. You may need to add an extra / to replace the .git for the URL to properly resolve.

- If the user specifies an invalid timeout in the request URL, the request will be aborted with an HTTP 400.

* fix parse devicePath issue on Azure Disk ([#74499](https://github.com/kubernetes/kubernetes/pull/74499), [@andyzhangx](https://github.com/andyzhangx))
* kubeadm: fixed nil pointer dereference caused by a bug in url parsing ([#74454](https://github.com/kubernetes/kubernetes/pull/74454), [@bart0sh](https://github.com/bart0sh))

* [fluentd-gcp addon] Use the logging agent's node name as the metadata agent URL. ([#63353](https://github.com/kubernetes/kubernetes/pull/63353), [@bmoyles0117](https://github.com/bmoyles0117))

### Feature

- API request throttling (due to a high rate of requests) is now reported in client-go logs at log level 2.  The messages are of the form:`Throttling request took 1.50705208s, request: GET:<URL>` The presence of these messages may indicate to the administrator the need to tune the cluster accordingly. ([#87740](https://github.com/kubernetes/kubernetes/pull/87740), [@jennybuckley](https://github.com/jennybuckley)) [SIG API Machinery]

* Fix instance metadata service URL. ([#49081](https://github.com/kubernetes/kubernetes/pull/49081), [@brendandburns](https://github.com/brendandburns))

- Fixed a regression in `kubectl` and `client-go` discovery when configured with a server URL other than the root of a server ([#117495](https://github.com/kubernetes/kubernetes/pull/117495), [@ardaguclu](https://github.com/ardaguclu))

## Changelog since v1.12.5

### Other notable changes

* kubeadm: fixed nil pointer dereference caused by a bug in url parsing ([#74454](https://github.com/kubernetes/kubernetes/pull/74454), [@bart0sh](https://github.com/bart0sh))