Yesung was hit while performing for SS3 Singapore.
On this video you will see how suju's Yesung was being hit by a light stick or a pepper from the audience. The object thrown was unclear. Some people claim that they saw the object and it was a pepper but to be safe lets just call it a UFO (Unidentified Flying Object). Maybe the person who threw that "object" needs the attention of Yesung. He/She wins the attention of Yesung and all the ELFs out there. We hope Yesung was just fine.