Major macOS High Sierra Security Vulnerability Allows Full Admin Access Without Password, So Here Is A Fix For It

There is a serious bug discovered in macOS High Sierra that someone with physical access to a macOS machine can access and change personal files on the system without needing any admin credentials. The bug, found by developer Lemi Ergin, lets anyone log into an admin account using the username "root" with no password. 

This security vulnerability works when attempting to access an administrator's account on an unlocked Mac, and it also provides access at the login screen of a locked Mac. Which means Users who haven’t disabled guest user account access or changed their root passwords (likely most) are currently open to this vulnerability.

The first step to fixed the bug is disabling guest account access. This can make it more difficult for an attacker to jump in and change system settings. After you disabled guest access, the next step is to changing the system’s root password. This can put a stop to the vulnerability altogether. Here’s how!

1. Go to System Preferences, then click Users & Groups (or Accounts).
2. Click the lock icon, then enter an administrator name and password.
3. Then Click Login Options.
4. Click Join (or Edit).
5. Click Open Directory Utility.
6. Click the lock icon in the Directory Utility window, then enter an administrator name and password
7. Choose Edit > Enable Root User, then enter the password that you want to use for the root user.

It appears that this bug is present in the current version of macOS High Sierra, 10.13.1, and the macOS 10.13.2 beta that is in testing at the moment. It's not clear how such a significant bug got past Apple, but it's likely this is something that the company will immediately address.

Update:

“We are working on a software update to address this issue. In the meantime, setting a root password prevents unauthorized access to your Mac. To enable the Root User and set a password, please follow the instructions here. If a Root User is already enabled, to ensure a blank password is not set, please follow the instructions from the ‘Change the root password’ section.”

Via MacRumors And 9to5Mac, Image Credit MR And 9to5Mac