Karissa Shannon, who admits to doing a girl-on-girl sex tape with Heidi Montag, is staying mum about the XXX footage. However, her boyfriend Sam Jones III, isn't holding back his thoughts of Spencer Pratt ... who alleges he has the video.

Pratt is currently in Costa Rica awaiting a meeting with Steven Hirsch, president of Vivid Entertainment. The two are expected to discuss how much money the sex tape is worth. Reportedly, Heidi Montag is there, too.

Jones tells our X17 videographer that he "wants to whoop that a** in Costa Rica."

Watch your back, Spence!