If you check the EMC2 slack out they are working on the issue and the max lost on bittrex is 5K which. It also seems that the double spend is related to a buggy code. So hopefully they will be able to sort it out soon.
Quote From Slack
"There is one little light out there: as our investigation so far, it is very likely that those double spends are not being produced on purpose, but on buggy code."
"So the guy mining them might not even know about the dilemma."
From what I read it was 5k total which was impacted, and this was not even an intentional attack. Not the end of the world, and they caught the issue early. So no reason to panic.