Samsung Galaxy S5 Active (AT&T) (SM-G870A) Firmware Overview
The archive lists 2 official builds for the Samsung Galaxy S5 Active (AT&T) across 1 region (CSC). The newest one is G870AUCS2DQD1, released May 8, 2017 with Android . It is a security update on bootloader binary 2: once a phone runs it, firmware with a lower binary can no longer be flashed (how to read a build number).
How to Flash SM-G870A Firmware
Put the Samsung Galaxy S5 Active (AT&T) into Download Mode, load the BL, AP, CP and CSC files into Odin on a Windows PC and press Start. Pick a build with the same or a higher Bit than the one installed — a lower bootloader binary will be rejected.