([#123341](https://github.com/kubernetes/kubernetes/pull/123341), [@neolit123](https://github.com/neolit123))
- kubectl `port-forward` over websockets (tunneling SPDY) can now be enabled using an `Alpha` feature flag environment variable: KUBECTL_PORT_FORWARD_WEBSOCKETS=true. The API Server being communicated to must *also* have an `Alpha` feature flag enabled: PortForwardWebsockets.

### External credential provider for client-go

The client-go credential plugins can now be passed in the current cluster information via the `KUBERNETES_EXEC_INFO` environment variable. Learn more about this on [client-go credential plugins documentation](https://docs.k8s.io/reference/access-authn-authz/authentication/#client-go-credential-plugins/).

### CronJob controller v2 is available through feature gate

or `/etc/sysconfig/kubelet`, depending on the system you're running on.
([#64780](https://github.com/kubernetes/kubernetes/pull/64780), [@luxas](https://github.com/luxas))

- Adds `OpenAPIV3SchemaInterface` to `DiscoveryClient` and its variants for fetching OpenAPI v3 schema documents. ([#108992](https://github.com/kubernetes/kubernetes/pull/108992), [@alexzielenski](https://github.com/alexzielenski))

* AWS volumes: Use /dev/xvdXX names with EC2 ([#27628](https://github.com/kubernetes/kubernetes/pull/27628), [@justinsb](https://github.com/justinsb))
* Add a test config variable to specify desired Docker version to run on GCI. ([#26813](https://github.com/kubernetes/kubernetes/pull/26813), [@wonderfly](https://github.com/wonderfly))

- Alpha implementation of Kubectl Command Headers: SIG CLI KEP 859 enabled when KUBECTL_COMMAND_HEADERS environment variable set on the client command line. ([#98952](https://github.com/kubernetes/kubernetes/pull/98952), [@seans3](https://github.com/seans3))
- Base-images: Update to debian-iptables:buster-v1.4.0
  - Uses iptables 1.8.5

- New `KUBECACHEDIR` environment variable was introduced to override default discovery cache directory which is `$HOME/.kube/cache`. ([#109479](https://github.com/kubernetes/kubernetes/pull/109479), [@ardaguclu](https://github.com/ardaguclu))

- Kubeadm: make sure the extra environment variables written to a kubeadm managed PodSpec are sorted alpha-numerically by the environment variable name. ([#126743](https://github.com/kubernetes/kubernetes/pull/126743), [@neolit123](https://github.com/neolit123)) [SIG Cluster Lifecycle]

- Users should not rely on unsupported CRON_TZ variable when specifying schedule, both the API server and cronjob controller will emit warnings pointing to https://kubernetes.io/docs/concepts/workloads/controllers/cron-jobs/ containing explanation ([#106455](https://github.com/kubernetes/kubernetes/pull/106455),...

- The certificate signer no longer accepts ca.key passwords via the `CFSSL_CA_PK_PASSWORD` environment variable. This capability was not prompted by user request, never advertised, and recommended against in the security audit. ([#84677](https://github.com/kubernetes/kubernetes/pull/84677), [@mikedanese](https://github.com/mikedanese))