Samsung just recently started pushing a new security patch for their 3 year old Galaxy S5. The new version is labelled G900FXXS1CQH1 and is around 75 MB in size. It’s currently reached the units in Europe and should be hitting rest of the devices pretty soon.
Its predecessors on AT&T, the S6 active, S6, S6 edge and S6 edge+, are also getting the latest patch labelled as G890AUCS6DQH1, G925AUCS6EQH1 and G928AUCS4EQH1.
Nexus 6 units on AT&T are also receiving the August security update which is labelled as version N6F27I.
Source: GSMArena