You knew this was coming.

from www.tmz.com – TMZ has learned … newly-minted porn star Montana Fishburne allegedly beat the hell out of her boyfriend’s ex and is being prosecuted for assault with a deadly weapon.

Montana was arrested last February after allegedly barging into the alleged victim’s home (the complaint does not give her name), forcing her into the bathroom and beating the crap out of her. We’re told the victim had “significant injuries.”

The L.A. City Attorney’s Office has charged Fishburne with battery, and will be adding charges of false imprisonment and assault with a deadly weapon.

Montana, who’s being repped by the effervescent Shawn Chapman Holley, has pled not guilty and the case is pending.

Fishburne’s boyfriend, Jerome Greene, was also charged in the attack against his ex-girlfriend but already pled no contest to domestic battery.

As for Montana — who is releasing her first sex tape through Vivid Entertainment — she has big problems. She was arrested last November for prostitution. Montana pled no contest to the lesser charge of criminal trespass and was placed on probation. The judge could use the pending case to violate her probation.