Samsung Galaxy S8 and Galaxy S8+ units on T-Mobile are receiving a new update today that includes the July security patch. The update weighs in at roughly 136MB, so it seems like there should be more than that, though it doesn’t look like there is.
T-Mobile says the new software versions are G950USQU1AQGA (S8) and G955USQU1AQGA (S8+) and that you should also expect a “UMTS 911 update.” That’s it.
The updates are live now. To grab them, head into Settings>System update.