A vulnerability within MacOS High Sierra was discoverd: It allowes logins and/or changes to critical Settings with the Superuser (root) without a password.
I’m sure that Apple is already working on a permanent fix for that, until then you should safe your Mac!
Howto fix the macOS blank root password Security issue?
- Open ‘Terminal’ or ‘iTerm2’
- Type ‘sudo passwd root’
- Type your (User) password
- Select a strong password for root (and repeat it)