If you remember, a while ago we found out that setting preferredIndex = 3 for StaticPopupDialogs prevents it from tainting badly, recently 3 is not enough so the new thing is setting it to 4 or, if you want it future proof, you use the global var STATICPOPUP_NUMDIALOGS so if Blizzard raises it again, we are save.

Oh,ok, thank you for the warning!
I tend to not be very up-to-date on changes in the tainting scene.