The bug in MacOS High Sierra means anyone can gain entry to the computer without a password, giving them administrator rights.
In a statement, Apple said: “We are working on a software update to address this issue.”
The problem was made public by Turkish developer Lemi Ergin, who found by typing in the username “root”, not entering a password and hitting “enter” a few times, he could get unrestricted access to the system.
He described it as a “huge security issue”, adding the result was “unbelievable”.
In response, the Apple Support Twitter account asked him to direct message them, saying: “Let’s take a closer look at what’s happening together.”