Admin Center accessible without authentication
I have installed WAC on a cloud hosted server. It is possible to access the WAC page without providing any credentials using Chrome 77 (just click sign in without providing any credentials). WAC will show "NT AUTHORITY\ANONYMOUS LOGON” under Settings -> Account.
Ex: install WAC to listen on port 6000. Then try to access WAC using Chrome 77, pointing to https://contoso.com:6000/. When prompted for credentials, just click sign-in without providing any.