* The pod annotation  `security.alpha.kubernetes.io/unsafe-sysctls` allows customization of namespaced sysctls where isolation is unclear....

* kubectl exec now allows using resource name (e.g., deployment/mydeployment) to select a matching pod. ([#73664](https://github.com/kubernetes/kubernetes/pull/73664), [@prksu](https://github.com/prksu))
    * kubectl exec now allows using --pod-running-timeout flag to wait till at least one pod is running.

- Added a alpha feature, behind the `RelaxedEnvironmentVariableValidation` feature gate.
  When that gate is enabled, Kubernetes allows almost all printable ASCII characters to be used in the names
  of environment variables for containers in Pods. ([#123385](https://github.com/kubernetes/kubernetes/pull/123385), [@HirazawaUi](https://github.com/HirazawaUi))

### Other notable changes

* StatefulSet: Set hostname/subdomain fields on new Pods in addition to the deprecated annotations, to allow mitigation of Pod DNS issues upon upgrading to Kubernetes v1.7.x. ([#50942](https://github.com/kubernetes/kubernetes/pull/50942), [@enisoc](https://github.com/enisoc))
* Azure: Allow VNet to be in a separate Resource Group. ([#49725](https://github.com/kubernetes/kubernetes/pull/49725), [@sylr](https://github.com/sylr))

- kubeadm no longer allows using v1alpha3 configs for anything else than converting them to `v1beta1`. ([#74025](https://github.com/kubernetes/kubernetes/pull/74025), [@rosti](https://github.com/rosti))

(Alpha), allowing you to specify application-level metrics and thresholds to
trigger scaling up and down the number of pods in your application.
  * <strong>New GUI</strong> (dashboard) allows you to get started quickly and enables the same
functionality found in the CLI as a more approachable and discoverable way of
interacting with the system. Note: the GUI is enabled by default in 1.2 clusters.

- `kubelet` allows pods to use the `net.ipv4.tcp_fin_timeout`, “net.ipv4.tcp_keepalive_intvl”
  and “net.ipv4.tcp_keepalive_probes“ sysctl by default; Pod Security Admission
  allows this sysctl in `v1.29+` versions of the baseline and restricted policies. ([#121240](https://github.com/kubernetes/kubernetes/pull/121240), [@HirazawaUi](https://github.com/HirazawaUi))

  * Allow configuration of a single security group for ELBs ([#45500](https://github.com/kubernetes/kubernetes/pull/45500), [@nbutton23](https://github.com/nbutton23))

  * Remove check that forces loadBalancerSourceRanges to be 0.0.0.0/0. ([#38636](https://github.com/kubernetes/kubernetes/pull/38636), [@dhawal55](https://github.com/dhawal55))