https://qz.com/1141425/if-youre-running-macos-high-sierra-on-your-mac-update-it-as-soon-as-possible-aapl/

Yesterday, Nov. 28, security researchers broadcast across the web that there was a massive vulnerability within Apple’s latest computer operating system, macOS High Sierra. Essentially anyone could access anyone else’s Mac by entering a certain word on the login screen, leaving the password field blank, and, eventually, the computer would let them in.

Apple told Quartz yesterday that it was aware of the problem, and today, the company has issued a patch to its software that allegedly fixes the vulnerability, as 9to5Mac first spotted. Anyone running macOS High Sierra version 10.13.1 should update their software as soon as they can through the Mac App Store. (People running older versions of macOS were not affected by the bug.)