macOS High Sierra ‘root’ security bug reappears if you recently upgraded from macOS 10.13 to 10.13.1
Update 12/1/2017: A Wired report states that users of macOS 10.13 High Sierra who installed the root security update will need to reinstall the update and restart the Mac if the operating system is upgraded to macOS 10.13.1 High Sierra. Apple has details in a support document to see if the update has properly installed.
Update 11/29/17: Apple has released an official fix for the issue via a security update. You can install the update by launching the App Store app, and then click on Updates. Press Command-R to reload the Updates page to see new updates. It will appear as “Security Update,” and you can click on the Update button to install it. Your Mac does not need to restart.