The authenticator: probably the title of a future Dwayne Johnson flick, also the preserve of banks and Blizzard. This extra measure of security for your battle.net account is available as both a physical widget and an iPhone app - and an upcoming iOS update may cause the latter to reset.
If it does, it’s going to be a real pain in the bum.
Thankfully, there are things you can do. Firstly, Blizzard recommend that you sign up to their SMS Protect service. Sounds like a police notification system, is actually a means of removing an old authenticator from your account using a texted security code.
Secondly, it’s possible to detach your authenticator from your account before updating. To do that, you’ll need to contact Blizzard Web Chat by clicking through about four different pages: Battle.net > I have an issue managing my account > I want to remove my authenticator > Live chat.
After that, you’ll want to take the good, old-fashioned write-a-thing-down approach. Note your authenticator’s serial number and restore code on something that isn’t your phone before the update, and take a screenshot - that way you can relink your authenticator to your account when the OS update concludes.
And finally: update over wi-fi. Blizzard have found that phones updated by other means are more prone to accidental resets.
You’ve but a few days to make your preparations before the update hits. Whether you be WoWer, witch doctor or Terran specialist: godspeed, friends.