https://qz.com/1140320/apples-macos-high-sierra-has-a-ridiculously-simple-security-flaw-that-lets-anyone-log-into-any-mac-aapl/

If you have an Apple computer running the latest version of the company’s software, macOS High Sierra, be warned: It might be possible for someone to quite easily get into your computer without your login credentials.

Without explaining what the actual bug is (we don’t want to make it any easier for potential hackers than this already is, and you can find it on Twitter pretty easily), someone can login to a Mac by typing a word in the login field, leaving the password field blank, and attempting to log in several times. Eventually the system will let you in with full access, according to security researchers.