'An attacker can bypass the authentication without a password,' wrote Apple's security site. 'Logical errors are in authentication and have been fixed'. Apple also confirmed that only macOS High Sierra is affected.
The reason why Apple fixes the problem in just 24 hours is because this error makes users more likely to experience serious risks. On Unix systems like macOS, 'root' is the highest user right, capable of changing anything on the operating system.
'When someone logs into a Mac with root access, they can do anything, including file access, installing spyware . In other words, just don't keep an eye on the Mac for 30 seconds, someone can take control and use it later, 'Mac security researcher Thomas Reed said.
The cause of this error is also clearly presented by Patrick Wardle, director of research at Synack here.https://objective-see.com/blog/blog_0x24.html