If you’re running macOS High Sierra, stop and do this now to fix the root access vulnerability.

Update: Apple has released a fix. Security Update 2017-001. Install the update:

  1. Click Apple icon in menu bar
  2. Go to App Store
  3. Updates
  4. Install security update 2017-001 (Doesn’t require a reboot.)

No further action required.

Alternative solutions achieve the same outcome

  1. Open Spotlight Search, click the magnifying glass icon in the upper-right corner of the menu bar, or press Command-Space from any app
  2. Start typing the first few letters of Directory Utility and press Return.
  3. In Directory Utility, click on the Lock (🔒) icon.
  4. Enter your Password.
  5. Click on Edit in the menubar.
  6. Click on Enable Root User.
  7. Enter and confirm your Root User Password. Use a password manager e.g. 1Password or Lastpass to generate a strong, unique password.

If you prefer the command line, you can

  1. Launch Terminal.
  2. Type: sudo passwd -u root
  3. Enter and confirm your Root User Password. Use a password manager e.g. 1Password or Lastpass to generate a strong, unique password.

Do not disable the Root User. That just blanks the password and allows the exploit to work again.