The case could actually be cracked around the post, or the post itself may be loose, causing the acid to leach around the post. Remove the battery and clean it and the tray area with battery acid neutrilizer (or just use baking soda/water). Check the post area very well and reinstall if nothing obvious is found.

I just had to do all of that when I forgot the trickle charger was on and acid leaked out the vent tube. I was more concerned with the battery box and underneath area than with the battery itself.