Recently there was a problems in multiplayer:
Because a mechanic in the Golden Horde was almost never used, no one noticed it came with a bug that could be exploited to make infinite units with no cost at certain conditions.
Now that everyone has started sharing it widely, and there are even 4v4 ranked matches featuring only Golden Horde players, an official message has been released:
WARNING!
Apparently, the exploit is now illegal in ranked matches, with a ban warning and they will attempt to fix it in the coming days.
Anyway, just to let you know, in case anyone accidentally uses it.
Cheers.