I know you fellow HTC One users out there are getting antsy for your Android 4.3 update. Sure, there was a leaked build that showed up last month that developers got a hold of and made it a into flashable zip file for your phone, but you are waiting for the ACTUAL update. Well AT&T HTC One users, this is as close as you are going to get as of now.
Last night it seems that a developer by the name of Birdman, dropped Android 4.3 build number 3.10.502.2 on the Rootzwiki forums, but sadly it is only for AT&T users. So if you want to give it a shot, you have your choice to use the RUU method, or you can just flash it like a normal ROM. Proceed with caution as always, and follow directions carefully. Let us know how it is.