Latest Samsung Galaxy S5 (SM-G900A) - ATT firmware
Samsung Galaxy S5 (SM-G900A) firmware for USA (AT&T) (ATT): 1 build in the SamMobile archive, newest first. The latest is G900AUCU1ANCE (Android 4.4.2, built 14 March 2014). Open a build to download it, or switch region with the country selector.