Baby Zombies can attack through doors.

Baby zombies have the ability to attack through closed doors.
I have taken 2 screenshots where there were baby zombies on the other side of the door and you can (sort of) see that I was attacked.
Have not tested with zombie pigmen, since they don't attack doors or with other transparent blocks, as zombies don't attack them.
Tested on 1.6.2 snapshot, normal difficulty.
Still happens in release.