- Kubeadm: during the validation of existing kubeconfig files on disk, handle cases where the "ca.crt" is a bundle and has intermediate certificates. Find a common trust anchor between the "ca.crt" bundle and the CA in the existing kubeconfig on disk instead of treating "ca.crt" as a file containing a single CA. ([#123102](https://github.com/kubernetes/kubernetes/pull/123102), [@astundzia](https://github.com/astundzia))

- Kubeadm: changed the "system:masters" Group in the apiserver-kubelet-client.crt certificate Subject to be "kubeadm:cluster-admins" which is a less privileged Group. ([#121837](https://github.com/kubernetes/kubernetes/pull/121837), [@neolit123](https://github.com/neolit123))