Do not allow all requests.
Setting admission control plugin 'AlwaysAdmit' allows all requests and do not filter any requests.
The 'AlwaysAdmit' admission controller was deprecated in Kubernetes v1.13. Its behavior was equivalent to turning off all admission controllers.
Only requests explicitly allowed by the admissions control plugins would be served.
Edit the API server pod specification file '/etc/kubernetes/manifests/kube-apiserver.yaml' on the master node and either remove the '--enable-admission-plugins' parameter, or set it to a value that does not include 'AlwaysAdmit'.