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.”
The issue was first reported this afternoon and was reproduced by Dave Mark at The Loop.