If you are in survival mode, and get mobs angry at you (punch wolf, get near zombies, skeletons, etc) and then switch over to spectator mode. They will continue to be angry at you. Creepers will blow up
Environment
Windows 7 Home Premium
java version "1.7.0_45"
Java(TM) SE Runtime Environment (build 1.7.0_45-b18)
Java HotSpot(TM) 64-Bit Server VM (build 24.45-b08, mixed mode)
Duplicate of MC-46596 - If you have not, please use the search function in the future, to see if your bug has already been submitted. If you could not find the original report, please comment with the keywords you searched for.