The cover group is comprised of eleven Thai members and one Korean and they've gained a lot of popularity by covering EXO's dances and songs.
As they have over 90,000 members in their fan club, they've held fan meetings and made TV appearances in their country - even hosting an event in Indonesia! Although it'd be fine if the group just stopped at doing covers, but for every event, they've been using EXO's group logo, poster, and album designs, as well as selling merchandise.
Due to EXO fans' complaints, Millenium Boy uploaded an explanation and apology onto their YouTube channel, basically saying, "The money we received during our fan meeting was used for our event. We made and sold clothes, bracelets, and hats because we were following our fans' requests; we didn't make them with the intention of commercial profit." They also explained that their seemingly belittling attitude towards EXO members in their various social media posts were not intended that way.
A rep from SM Entertainment stated, "It is illegal to use EXO's intellectual property without permission, so we plan on taking action in the future regarding their commercial promotions."
[Update - SM has now decided to let the group off the hook for the time being. Read about it in the latest article here.]