Attacker shouted something about Chris Brown
Rihanna was not seriously injured in a fall caused when a madman attacked her as she was leaving a London club. The man threw a full drink bottle at Rihanna after shouting something about Chris Brown. Rihanna fell trying to avoid the projectile (which by some reports did not strike her) and had to go to hospital to be treated and then released.
The attacker was not apprehended, which is a little surprising.
Further Reading
DNA India: Rihanna injured by fan
Hollywood Gossip: Rihanna injured in bottle attack!
Yahoo UK: Rihanna hit after crazed fan chucks bottle at her, slices open her leg
Photo courtesy of The Examiner: Rihanna Injured