- Kubectl version changed to write a warning message to stderr if the client and server version difference exceeds the supported version skew of +/-1 minor version. ([#98250](https://github.com/kubernetes/kubernetes/pull/98250), [@brianpursley](https://github.com/brianpursley)) [SIG CLI]

* fixes configuration error when upgrading kubeadm from 1.9 to 1.10+ ([#62568](https://github.com/kubernetes/kubernetes/pull/62568), [@liztio](https://github.com/liztio))
    * enforces  kubeadm  upgrading kubernetes from the same major and minor versions as the kubeadm binary.
* Bugfix allowing use of IP-aliases with custom-mode network in GCE setup scripts. ([#62172](https://github.com/kubernetes/kubernetes/pull/62172), [@shyamjvs](https://github.com/shyamjvs))

* Add automatic etcd 3.2->3.1 and 3.1->3.0 minor version rollback support to gcr.io/google_container/etcd images. For HA clusters, all members must be stopped before performing a rollback. ([#59298](https://github.com/kubernetes/kubernetes/pull/59298), [@jpbetz](https://github.com/jpbetz))

- New flag `--show-hidden-metrics-for-version` in kube-proxy, kubelet, kube-controller-manager, and kube-scheduler can be used to show all hidden metrics that are deprecated in the previous minor release. ([#85279](https://github.com/kubernetes/kubernetes/pull/85279), [@RainbowMango](https://github.com/RainbowMango)) [SIG Cluster Lifecycle and Network]

#### Features graduated to beta:

* addon-resizer flapping behavior was removed. ([#46850](https://github.com/kubernetes/kubernetes/pull/46850), [@x13n](https://github.com/x13n))
* Change default `httpGet` probe `User-Agent` to `kube-probe/<version major.minor>` if none specified, overriding the default Go `User-Agent`. ([#47729](https://github.com/kubernetes/kubernetes/pull/47729), [@paultyng](https://github.com/paultyng))

### SIG Network

For 1.13, the areas of focus were in IPv6, DNS improvements and some smaller items:

 - Performance improvements for collections of metrics and summary

### Increase the Kubernetes support window to one year

As of Kubernetes 1.19, bugfix support via patch releases for a Kubernetes minor release has increased from 9 months to 1 year.

- The `gcp` and `azure` auth plugins have been restored to client-go and kubectl until https://issue.k8s.io/111911 is resolved in supported kubectl minor versions. ([#111918](https://github.com/kubernetes/kubernetes/pull/111918), [@liggitt](https://github.com/liggitt))

### Documentation

* Protobuf serialization does not distinguish between `[]` and `null`.