Apple has released the crisp version of Mac OS High Sierra 10.13.3 to the public on Tuesday evening.
This time, focus is solely on bug and security fixes, including resolving a problem that could lead to that conversations in the message were temporarily listed in the wrong order. We can probably assume that there is also some correction that has with the Spectre and Meltdown security holes.
If you want to download the update, just go to the Mac App Store. As usual, it may be a wise idea to back up important files before installation.