AT&T’s variant of the HTC One is getting a petite maintenance update as we speak. As such (maintenance update), it doesn’t add a lot of new things to the mix, quite the contrary. It is said that this release is all about LTE enhancements which should (obviously) increase your upload and download speeds. Moreover, we’re hoping that some performance and stability tweaks are also included in the new firmware, version 1.26.502.15.
According to this XDA thread, we’re talking about a 245MB-heavy download, so you’re better off “pushing the button” while connected to your local Wi-Fi hotspot to make this a seamless process. Also make sure your HTC One’s battery is fully charged to have enough juice for a successful update. Good luck.