Per Mac Rumors, there is a major security flaw in the High Sierra OS. If you are using a Mac and have the latest version (High Sierra), you need to go into the terminal and type:

sudo passwd root

High Sierra shipped with a bug in the GUI authentication system where you can login as root with no password by entering root in the username field and clicking the enter button twice rapidly. First time enables the account. Second time lets you in with full access to everything as a superuser.

This exploit was published yesterday, and if screen sharing (Mac version of remote desktop) is enabled, it works there too.

Setting a password for root solves the bug. We are not Mac folk here at Coho, but this post will give you the instructions you need:

https://www.macrumors.com/2017/11/28/macos-high-sierra-bug-admin-access/