Apple has released a macOS security update to fix a major login security flaw.

Apple just released a security update for macOS High Sierra, and you should update it right now. This update fixes a vulnerability that was discovered yesterday that allowed someone to log into your Mac without your password.

To install the update, open the Mac App Store and go to the «Updates» tab. Interestingly, the release notes state, «Install this update as soon as possible.» Apple has been working long hours to fix yesterday’s flaw as soon as possible. But this shouldn’t have happened in the first place.

The security flaw affected all Macs running the latest version of High Sierra (at least version 10.13.1 — 17B48). From the login screen or the preference pane, you can bypass all security screens by entering the root username and password. After doing so, you can see everything on the computer, even if it’s not yours. This even works with a screen sharing session. This is a great way for hackers to access your emails, personal data, and more.

The release notes for the patch are quite short. «A logic error existed in credential validation. This has been addressed with improved validation,» Apple says.

Update: Apple will automatically roll out the update later today to everyone affected. Apple issued the following statement:

«Security is a top priority for every Apple product, and unfortunately, we have encountered issues with this version of macOS.

When our security researchers learned of the issue on Tuesday afternoon, we immediately began working on an update to patch the security hole. This morning, as of 8:00 AM, the update is available for download, and starting today, it will be automatically installed on all systems running the latest version (10.13.1) of macOS High Sierra.

We deeply regret this error, and we apologize to all Mac users, both for releasing this vulnerability and for the concern it raises. Our customers deserve better. We are reviewing our development processes to prevent this from happening again.»