Never had this happen before but the lid for Super Tripel fermenter decided it was tired of being attached overnight. I guess the 3787 strain is rather aggressive even with the Fermcap S in the boil. I scooped out a bit of the krausen to make some room and put the lid back on since I did not have the stuff to do a blow off hose. I dropped the temperature down to 68 as well to keep it under control and hopefully all will be well now.