Latest Samsung GALAXY S4 (SGH-I337) - ATT firmware
Samsung GALAXY S4 (SGH-I337) firmware for USA (AT&T) (ATT): 2 builds in the SamMobile archive, newest first. The latest is I337UCUAMDL (Android 4.2.2, built 27 April 2013). Open a build to download it, or switch region with the country selector.