'Big Brother' Houseguests Furious Over Unwanted Butt Poking

Several "Big Brother" competitors are claiming their butts are being violated by a fellow houseguest for weeks -- who's been captured on video jamming her fingers into various dumpers without consent.

The anal invader is Jessica Graf -- whose schtick is to approach unsuspecting houseguests from behind and surprise them with a deep oil check.

Graf has been recorded pulling the move on Paul and Matt -- who were upset about it and confronted Jessica. Problem is, she laughed it off as a joke.

Another female houseguest, Alex, claims Jessica pulled the same move on her -- poking her in the butt and the vagina.

During a live feed from the house, Alex got emotional when describing the incidents to houseguest Josh -- and said it affected her because a family member had been raped and killed.

Paul and Kevin have discussed Jessica's actions in the house -- and said if she was a man poking women, she would be in jail for sexual assault.

We reached out to CBS for comment. So far, no word back.