root account locking after installation
By default the password for the root user is expired instead of a locked account or similar. A regular 'su -' will show a password changing prompt, allowing anyone to set a root password without previous authentication (eg. if a machine is left unattended and unlocked).
Instead the account should be locked or, if not possible due to scripts requiring this state, have a random password (like in Ubuntu), requiring user authentication prior to changing the password.