Quote from DecenaI searched through FrameXML and the Blizzard addons for both variables, and they are only set in two places, neither of which was a function, so DHUD3 couldn't be modifying them like that either.
How could it be tainting these variables? I can't even begin to guess.
They are tainted exactly where the log says, at UIParent.lua:1298
_G[index] = yOffset; -- here index can be "CONTAINER_OFFSET_Y" or "PETACTIONBAR_YPOS"
Did you post the full taint log ? Because I don't see how the execution path has been tainted prior to this global var being tainted.