When I got on an untamed horse, the horse walked around for a while, but it did not buck me off. After two minutes of this, I tried getting off and getting back on, which also did not seem to affect the horse. Feeding the horse apples did not work, and neither did logging off and logging back on. This is a hardcore game in Minecraft 15w43c.

Steps to Reproduce:
1: Log onto a hardcore survival game.
2: Press the use button with an empty hand when facing a horse.
3: Wait for 2-3 minutes.