an integer value identifying a Unicode code point.
A rune literal is expressed as one or more characters enclosed in single quotes,
as in <code>'x'</code> or <code>'\n'</code>.
Within the quotes, any character may appear except newline and unescaped single
quote. A single quoted character represents the Unicode value
of the character itself,
while multi-character sequences beginning with a backslash encode
values in various formats.
</p>

<p>

### Action Required

* action required: the API server and client-go libraries have been fixed to support additional non-alpha-numeric characters in UserInfo "extra" data keys. Both should be updated in order to properly support extra data containing "/" characters or other characters disallowed in HTTP headers. ([#65799](https://github.com/kubernetes/kubernetes/pull/65799), [@dekkagaijin](https://github.com/dekkagaijin))

### Auth

- Fixed OpenID Connect (OIDC) token refresh when the client secret contains a special character. ([#76914](https://github.com/kubernetes/kubernetes/pull/76914), [@tsuna](https://github.com/tsuna))

### Action Required

* action required: the API server and client-go libraries have been fixed to support additional non-alpha-numeric characters in UserInfo "extra" data keys. Both should be updated in order to properly support extra data containing "/" characters or other characters disallowed in HTTP headers. ([#65799](https://github.com/kubernetes/kubernetes/pull/65799), [@dekkagaijin](https://github.com/dekkagaijin))

### Action Required

* action required: the API server and client-go libraries have been fixed to support additional non-alpha-numeric characters in UserInfo "extra" data keys. Both should be updated in order to properly support extra data containing "/" characters or other characters disallowed in HTTP headers. ([#65799](https://github.com/kubernetes/kubernetes/pull/65799), [@dekkagaijin](https://github.com/dekkagaijin))

- The etcd client library vendored in v1.16 (github.com/coreos/etcd/clientv3) has a bug where IPv6 IP addresses get incorrectly trimmed to the first occurance of the `:` character. This affects all users of the client library including the kube-apiserver and kubeadm. We are targeting the fix for this bug in v1.16.3. ([#83550](https://github.com/kubernetes/kubernetes/issues/83550))

## Urgent Upgrade Notes

- The API server and client-go libraries have been fixed to support additional non-alpha-numeric characters in UserInfo "extra" data keys. Both should be updated in order to properly support extra data containing "/" characters or other characters disallowed in HTTP headers. ([#65799](https://github.com/kubernetes/kubernetes/pull/65799), [@dekkagaijin](https://github.com/dekkagaijin)) Courtesy of SIG Auth

- Fixed EndpointSlice port name validation to match Endpoint port name validation (allowing port names longer than 15 characters) ([#84481](https://github.com/kubernetes/kubernetes/pull/84481), [@robscott](https://github.com/robscott))

  // Defaulted to nil.
  // +optional
  optional bool immutable = 4;

  // Data contains the configuration data.
  // Each key must consist of alphanumeric characters, '-', '_' or '.'.
  // Values with non-UTF-8 byte sequences must use the BinaryData field.
  // The keys stored in Data must not overlap with the keys in
  // the BinaryData field, this is enforced during validation process.

- Kubeadm: external etcd endpoints passed in the `ClusterConfiguration` that have Unicode characters are no longer IDNA encoded (converted to Punycode). They are now just URL encoded as per Go's implementation of RFC-3986, have duplicate "/" removed from the URL paths, and passed like that directly to the `kube-apiserver` `--etcd-servers` flag. If you have etcd endpoints that have Unicode characters, it is advisable to encode them in advance with tooling that is fully IDNA compliant. If you don't...