Apple said it is working to fix an issue that allows someone to login as a root user when they have access to your machine.
“We are working on a software update to address this issue,” an Apple spokesperson said in a statement provided to The Loop. In the meantime, setting a root password prevents unauthorized access to your Mac. To enable the Root User and set a password, please follow the instructions here: https://support.apple.com/en-us/HT204012. If a Root User is already enabled, to ensure a blank password is not set, please follow the instructions from the ‘Change the root password’ section.”