In 18w49a, if you shoot a firework with crossbow and hit a mob, the firework will explode immediately, but the damage source isn't the crossbow user, it will lead to:
1.if you shoot a firework with crossbow and hurt a neutral mob, it won't attack you back
2.if you shoot a firework with crossbow and kill a mob, it won't drop experience orb
3.if you shoot a firework with crossbow and kill a illager captain, you won't get a bad omen
......And more