Zombies attacked me through the walls. So I made a simple EXP farm by replacing the floor of a dungeon with magma cubes, I put water in it to move them, the widest area is at their feet at only half a block high so not even the baby zombies could get out. I stood about two blocks away and continually attacked them thus gaining experience. On more than one occasion both before and after the recent updates the zombies were able to attack me when I was easily two or more blocks away. I play in normal mode so I know for a fact that I didn't starve.