The Android 4.4 KitKat update has already leaked for the International LTE variant of the Galaxy S4 (I9505) and today there is a new leak for the AT&T model (I337). The leak comes from a thread at XDA-Developers.com and you can use ODIN to flash the firmware file once downloaded, there is also a One Click Zip format but it isn’t everyone’s cup of tea, so I suggest to go with the tradtional ODIN method. The firmware carries a Build Number I337UCUFMLD along with 2nd January 2014 as the Build Date, so it isn’t as new as the one for the International LTE Galaxy S4 (I9505).
The firmware is a test build so don’t expect it to be perfect or stable at all, there are a few small bugs along with some major ones like – Rebooting of the device on Video Playback. Also the firmware has new boot-loaders, which may create problems if you wish to go back to an Android 4.3 firmware later on and Rooting your phone will also stay on halt till there is a method introduced by a Developer to do so on Android 4.4 for AT&T Galaxy S4.
If you still wish to go ahead and flash this firmware via ODIN then you can download the file from this Link
