This could mean a bajillion different things, technically. However I'm going to stick with my initial assumption: An exploit.
Agreed, but here's hoping its an exploit fix!
I was a bit curious at the 'casual' wording of the fix.
Some of the 5 set bonus exploits that were being reported, talked exactly about 'item set bonuses.... not being removed properly'.. after un-equipping a given set!!
i.e. double mundus, hist bark, willows, eternal hunt etc....