For example:
A skeleton hide under a tree trying not to burn in daylight, but when a wild player appears, the skeleton start targetting and shooting the player and strafing around like supposed in a previous snapshot.
The problem is that they ignore the danger (in this case, sunlight) and start strafing to it.

And then the Skeleton burns and dies...

This also makes it fall off cliffs, try to swim in lava, burn in daytime (explained), walk to cactus and fire.

Not only affect 15w47c, I don't know when this bug started...