T-Mobile customers who are carrying the Samsung Galaxy S8 or S8 Plus, there is a new software update that has been released for you. The update brings the December Android Security Update to the devices but nothing else is mentioned in the release notes by T-Mobile. It likely contains some performance fixes and bug fixes, especially given the size of the update files.
For the Galaxy S8, your new build is G950USQS2BQL1 and is 130.66MB in size. For S8 Plus owners, you are getting build G955USQS2BQL1 and it is slightly smaller at 127.11MB. The updates have been released by T-Mobile so you should start seeing the OTA updates for them as soon as today.
In most cases, with only the monthly Android Security Update involved, most updates will come in at less than 100MB. Given the slightly larger size for these on T-Mobile, it likely contains some fixes for both the devices but they may be so minor that they aren’t worth mentioning in release notes. In any event, owners of the Samsung Galaxy S8 and S8 Plus on the carrier should get the update installed when it becomes available to them to assure you have the latest-and-greatest security on your phone.
If you want to manually check for the update, you can do so by going into Settings and checking for the update.