- 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))

  
  1. `apiGroup`: If set, it must be a valid DNS subdomain (e.g. 'example.com').
  2. `kind` and `name`: It must be valid path segment name. It may not be '.' or '..' and it may not contain '/' and '%' characters. ([#125218](https://github.com/kubernetes/kubernetes/pull/125218), [@carlory](https://github.com/carlory))
- Enabled kubectl to find `kubectl-create-subcommand` plugins when positional

- Limit vSphere volume name to 63 characters long. ([#100404](https://github.com/kubernetes/kubernetes/pull/100404), [@gnufied](https://github.com/gnufied))

- Volume mount cleanup now considers only plugin directory and not the entire kubelet root ([#112607](https://github.com/kubernetes/kubernetes/pull/112607), [@mattcary](https://github.com/mattcary))
- `kubectl` now escapes terminal special characters in output. This fixes CVE-2021-25743.
   ([#112553](https://github.com/kubernetes/kubernetes/pull/112553), [@dgl](https://github.com/dgl))

### Other (Cleanup or Flake)

## Changelog since v1.18.16

## Changes by Kind

### Failing Test

- Fix handing special characters in the volume path on Windows ([#99138](https://github.com/kubernetes/kubernetes/pull/99138), [@yujuhong](https://github.com/yujuhong)) [SIG Storage]

### Bug or Regression

        Unicode encodings (UTF-8, UTF-16-BE, UTF-32-BE)
    *   Add "unit" attribute to the substr op, which allows obtaining the
        substring of a string containing unicode characters.
    *   Broadcasting support for Ragged Tensors.
    *   `SpaceToDepth` supports uint8 data type.
    *   Support multi-label quantile regression in estimator.

* Resolves regression generating informers for packages whose names contain `.` characters ([#82410](https://github.com/kubernetes/kubernetes/pull/82410), [@nikhita](https://github.com/nikhita))

## Changelog since v1.20.4

## Changes by Kind

### Failing Test

- Fix handing special characters in the volume path on Windows ([#99008](https://github.com/kubernetes/kubernetes/pull/99008), [@yujuhong](https://github.com/yujuhong)) [SIG Storage]

* 📝 Update docs for handling HTTP Basic Auth with `secrets.compare_digest()` to account for non-ASCII characters. PR [#3536](https://github.com/tiangolo/fastapi/pull/3536) by [@lewoudar](https://github.com/lewoudar).