UPDATE: Apple has posted a security update. 2017-001

Root-a-pocalyse. Root down. Root a toot toot. Many funny tweets today about a very serious issue. A bug was discovered in macOS 10.13 that enabled anyone to login with a root account. With no password. Wow. Seriously. Yeah, that’s bad.

Bug discovered by Lemi Orhan Ergin.

I tested by clicking on the lock icon in System Preferences. Normally this requires an admin account. I was able to authenticate with “root” and no password. This actually also set root to no password. You can choose a password here and this makes it for you. How convenient. You can also login to the Mac via the login window. With root. And no password. Crazy.

If your Mac is off it’s safe. Not joking. If your FileVault protected drive is encrypted and your mac is turned off then you’re good. If you Mac is turned on and you’ve logged in at least once (or at least decrypted the drive on boot) then you’re not safe.

What can you do? Change the root password and set the shell to false. Until Apple fixes this. Should be anytime now. Or soon.

dscl . -passwd /Users/root “random or very secure password here”

dscl . -create /Users/root UserShell /usr/bin/false

Read a comprehensive explanation on Rich Trouton’s site:  Der Flounder blog