there’s a thread talking about this in general but not one in tech support that i could find, apologies for the dupe. battle.net is repeatedly attempting to update both main OW, the PTR client, and the installed OWL viewer. whatever the ‘update’ is very trivial, as it is over almost immediately, but will pop up the ‘application wants to make changes to your computer’ dialog which takes over the entire screen, so it’s pretty annoying.
the only workaround i have found so far is to just quit out of battle.net. it doesn’t seem to be affecting other installed games like WoW. i’ve already performed a scan/repair.