'Produce X 101' contestant Yoon Seo Bin is facing controversy after a netizen claiming to be a former classmate revealed the trainee was notorious bully in school.

The netizen, who said they had always been in the same grade, proved their relationship by uploading past school images of the trainee, even revealing Yoon Seo Bin's real name as Yoon Byung Hwi.

They then went on to confess that Yoon Byung Hwi, who was raised in the southern city of Gwangju, was known as a violent school bully, with his violent behavior starting in middle school and following him through high school as well.

Among the images the netizen shared, Yoon Seo Bin is seen underage drinking and smoking. There were also screen captures of social media posts where he repeatedly used vulgar language.

Meanwhile, Yoon Seo Bin's agency JYP Entertainment has yet to release a response in regards to the post's claims and distributed images.