The K League side used a variety of mannequins to partially fill the empty seats in their home ground, Seoul World Cup Stadium, for their first home match of the season yesterday.
Some sharp-eyed viewers noticed a few of them seemed a little different to the others and claimed online that they were sex dolls.
It was unknown whether or not that was accurate until the club issued a via Instagram today.
They lay partial blame on the company supplying them, but apologised to their fans for the oversight, vowed to rectify the situation and take measures to prevent it happening again.
Seoul won the round 2 home match in question 1-0 against Gwangju, after losing their season opener 3-1 away to Gangwon last week.