* Don't generate empty record for externalName service.
    * Add validation for upstreamNameserver port.
    * Update go version to 1.9.3.
* CRI: define the mount behavior when host path does not exist: runtime should report error if the host path doesn't exist ([#61460](https://github.com/kubernetes/kubernetes/pull/61460), [@feiskyer](https://github.com/feiskyer))

- When the cluster size is small and the scheduler doesn't get unscheduled Pods frequently, the scheduler doesn't try to reschedule Pods in some cases. ([#119784](https://github.com/kubernetes/kubernetes/pull/119784), [@sanposhiho](https://github.com/sanposhiho)) [SIG Scheduling and Testing]

## Dependencies

  - [Changelog since v1.18.17](#changelog-since-v11817)
  - [Important Security Information](#important-security-information)
    - [CVE-2021-25735: Validating Admission Webhook does not observe some previous fields](#cve-2021-25735-validating-admission-webhook-does-not-observe-some-previous-fields)
  - [Changes by Kind](#changes-by-kind-2)
    - [API Change](#api-change-1)
    - [Feature](#feature)
    - [Bug or Regression](#bug-or-regression-2)

- The extension API server can now dynamically discover the requestheader CA certificate when the core API server doesn't use certificate based authentication for it's clients. ([#66394](https://github.com/kubernetes/kubernetes/pull/66394), [@rtripat](https://github.com/rtripat))

### SIG Autoscaling

    * Action required:
    * Anyone who generated server cert for admission webhooks need to regenerate the cert. Previously, when generating server cert for the admission webhook, the CN value doesn't matter. Now you must set it to the DNS name of the webhook service, i.e., `<service.Name>.<service.Namespace>.svc`.

- Reduce default NodeStatusReportFrequency to 5 minutes. With this change, periodic node status updates will be send every 5m if node status doesn't change (otherwise they are still send with 10s).

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