https://techcrunch.com/2017/11/28/astonishing-os-x-bug-lets-anyone-log-into-a-high-sierra-machine/ >Wow, this is a bad one. On Macs running the latest version of High Sierra — 10.13.1 (17B48) — it appears that anyone can log in just by putting “root” in the user name field. This is a huge, huge problem. Apple will fix it probably within hours but holy moly. Do not leave your Mac unattended until this is resolved. >The bug is most easily accessed by going to Preferences and then entering one of the panels that has a lock in the lower left-hand corner. Normally you’d click that to enter your user name and password, which are required to change important settings like those in Security & Privacy.