Samsung is rolling out a new software update for the Galaxy S9+ today, bringing the latest security patch to the flagship device. This update is for those who are on Oreo of course, and it is currently rolling out in the Nordic countries. The software version is getting bumped to G965FXXS2BRK3 and it's unclear if the update brings more than just security fixes.
However, even if it's just the December security patch, this is quite an important update. The December 2018 patch fixes a whopping 40 vulnerabilities that affect Samsung's software, including vulnerabilities that could allow unauthenticated access to Secure Folder items and the Gallery app. It's not often that so many vulnerabilities are discovered in either core Android or Samsung's version of the OS, so we can expect Samsung to be rolling out the December patch to most of its recent devices as the days go by.
The Galaxy S9+ update is currently rolling out over Samsung Smart Switch, but it should soon be available over the air. The update should also come to the regular Galaxy S9 and expand to more countries in the next few days. You can update your device using the relevant firmware available in our database as an alternative to Smart Switch.
Edit: The regular Galaxy S9 is also getting the December update.