My new active just downloaded and installed a new update. I haven't seen anything about it here.... My active was rebooting a few times every 90 minutes. So far that has stopped...
I recently bought an unlocked (used) Samsung Galaxy s4 active on Ebay. (When I started up the phone, the start up screen displayed a "Custom" message with an open padlock.) I opened the box and set up the phone as usual, and it appears to be running on stock android 4.3 TouchWiz. A day later, I went into settings and checked for updates.