Update 1/20: Looks like AT&T let some update docs slip out where they shouldn't have been, and they've since been pulled. So if you don't see an update just yet, don't be surprised.

Original follows:

It's certainly no Lollipop (sadly), but AT&T has pushed out an update for its HTC One M8 today. While it's relatively minor in the grand scheme of things, the update does enable HD Voice on the handset, and brings it up to Android version 4.4.4 KitKat.