- The requested name did not match the set of authorized names (`x509.HostnameError`)
  - The error surfaced after attempting a connection contained one of the substrings: "certificate is not trusted" or "certificate signed by unknown authority". ([#120736](https://github.com/kubernetes/kubernetes/pull/120736), [@MadhavJivrajani](https://github.com/MadhavJivrajani))

- The `--certificate-authority` flag now correctly overrides existing skip-TLS or CA data settings in the kubeconfig file ([#83547](https://github.com/kubernetes/kubernetes/pull/83547), [@liggitt](https://github.com/liggitt))
### Cloud Provider

- Kubeadm: tolerate whitespace when validating certificate authority PEM data in kubeconfig files ([#86705](https://github.com/kubernetes/kubernetes/pull/86705), [@neolit123](https://github.com/neolit123)) [SIG Cluster Lifecycle]

  * Passing multiple values separated by a comma in a single --from-literal flag is no longer supported. Please use multiple --from-literal flags to provide multiple values.
* Fixed a bug where the --server, --token, and --certificate-authority flags were not overriding the related in-cluster configs when provided in a `kubectl` call inside a cluster. ([#39006](https://github.com/kubernetes/kubernetes/pull/39006), [@fabianofranz](https://github.com/fabianofranz))

- kubeadm: prevent PSP blocking of upgrade image prepull by using a non-root user ([#77792](https://github.com/kubernetes/kubernetes/pull/77792), [@neolit123](https://github.com/neolit123))
- kubeadm: fix "certificate-authority" files not being pre-loaded when using file discovery ([#80966](https://github.com/kubernetes/kubernetes/pull/80966), [@neolit123](https://github.com/neolit123))

- Kubeadm: fixed a bug when using `kubeadm init --dry-run` with certificate authority files (`ca.key` / `ca.crt`) present in `/etc/kubernetes/pki`) ([#108410](https://github.com/kubernetes/kubernetes/pull/108410), [@Haleygo](https://github.com/Haleygo))

  - The requested name does not match the set of authorized names (x509.HostnameError)
  - The error surfaced after attempting a connection contains one of the substrings: "certificate is not trusted" or "certificate signed by unknown authority" ([#120767](https://github.com/kubernetes/kubernetes/pull/120767), [@MadhavJivrajani](https://github.com/MadhavJivrajani)) [SIG Architecture and Cloud Provider]

  - The requested name does not match the set of authorized names (x509.HostnameError)
  - The error surfaced after attempting a connection contains one of the substrings: "certificate is not trusted" or "certificate signed by unknown authority" ([#120768](https://github.com/kubernetes/kubernetes/pull/120768), [@MadhavJivrajani](https://github.com/MadhavJivrajani)) [SIG Architecture and Cloud Provider]

  - The requested name does not match the set of authorized names (x509.HostnameError)
  - The error surfaced after attempting a connection contains one of the substrings: "certificate is not trusted" or "certificate signed by unknown authority" ([#120766](https://github.com/kubernetes/kubernetes/pull/120766), [@MadhavJivrajani](https://github.com/MadhavJivrajani)) [SIG Architecture and Cloud Provider]

### Introducing `RootCAConfigMap`

`RootCAConfigMap` graduates to Beta, separating from `BoundServiceAccountTokenVolume`. The `kube-root-ca.crt` ConfigMap is now available to every namespace, by default. It contains the Certificate Authority bundle for verify kube-apiserver connections.

### `kubectl debug` graduates to Beta

`kubectl alpha debug` graduates from alpha to beta in 1.20, becoming `kubectl debug`.