The Bug

Mobs riding large entities, such as a zombie riding a sniffer, can still attack players who are completely above the vehicle and out-of-range of the passenger.

How to reproduce

1. Summon a zombie and a sniffer, then execute /ride @e[type=zombie,limit=1] mount @e[type=sniffer,limit=1]
2. Build up 3 blocks from the sniffer's position
3. Check the range the zombie can attack you from