Apple has just released a Supplemental Update for the latest (2018) MacBook Pro model with Touch Bar. It’s available from the App Store, or for separate download from this page.
Apple hasn’t yet revealed what the update does, apart from saying that it “improves the stability and reliability”. I suspect that this contains security fixes, in particular in relation to its T2 chip, and will update this article when I know details.
As the update is 1.3 GB in size, there is obviously quite a lot in it.
It is not intended for current MacBook Pro models which don’t have a Touch Bar, though.