([#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.

- 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))

    public void addDocumentSettingRewriteRule(final UnaryOperator<String> rule) {
        docSettingRewriteRuleList.add(rule);
    }

    /**
     * Gets the resource path for configuration files, checking type-specific variants first.
     *
     * @param basePath the base path for resources
     * @param type     the search engine type
     * @param path     the relative path to the resource
     * @return the full resource path
     */

- 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 key of the message: System Info */
    public static final String LABELS_system_info_configuration = "{labels.system_info_configuration}";

    /** The key of the message: Environment Variable Properties */
    public static final String LABELS_system_info_env_title = "{labels.system_info_env_title}";

    /** The key of the message: System Properties */

- 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))

- Added namespace access support to the CEL expressions of ValidatingAdmissionPolicy via a `namespaceObject`
  variable with expressions. ([#118267](https://github.com/kubernetes/kubernetes/pull/118267), [@cici37](https://github.com/cici37)) [SIG API Machinery and Testing]

        activated. On the other hand, {@code exists} will test for the existence of the file and if it is
        there, the profile will be activated.
        <p>Variable interpolation for these file specifications is limited to {@code ${project.basedir}},
        system properties and user properties.&lt;/p></description>
      <fields>
        <field>
          <name>missing</name>

    * inherit the environment from the primary process, so if the container was created with tty=false,that means the exec session's TERM variable will default to "dumb". Users can override this by setting TERM=xterm (or whatever is appropriate) to get the correct "smart" terminal behavior.