In a Nintendo briefing this week, it was announced that Mario Kart 7 will soon be patched. Nintendo of Europe bossman Satoru Shibata stated the game will receive a few gameplay tweaks and fix an online exploit in the Wuhu Mountain Loop track.
The glitch apparently was a real bummer for those who play online, but since I avoid all human contact even on a virtual basis I would have no idea. There were no other details other than that players should expect the update through the eShop sometime in "mid-May".
Mario Kart 7 patch coming "mid-May" [Official Nintendo Magazine]