"AT&T 4.3 update has officially begun to push. You should see it thru the ATT sw update," tweeted Jason Mackenzie, president of HTC America.
"Have seen others commenting about having downloaded it," he wrote in another tweet.
Verizon customers at least received Android 4.2.2 pre-installed when the phone finally came to the nation's No. 1 network. But all other major U.S. carriers launched the HTC One with Android 4.2.
We've asked HTC, Verizon and T-Mobile when Android 4.3 would be available to download on their respective networks and will update this story when we hear back.
Android 4.4 KitKat right around the corner
HTC isn't going to get a break from customers who want the Android 4.4 KitKat version of Google's operating system.
Although the Android 4.3 update includes notable improvements like Bluetooth 4.0, restricted profiles, and a reworked camera user interface, KitKat is rumored to be right around the corner.
Android 4.3 launched with the Nexus 7 tablet toward the end of July, meaning it took just over two months for half of the major U.S. carriers to deliver the update.
That means existing device owners who are also Android 4.4 hopefuls may have to wait until next year for the next big update, even if it's announced this month.
- Read about how Android SMS Hangouts is going to finally rival iMessages.