The tape was reportedly posted to Tygasworld.com for 30 minutes before being taken down.
"Tyga will not sign off on releasing it to the masses, but Kylie is scared that a sex tape could get in the wrong person's hands with one of his buddies and they could put it online to embarrass her," a source told the Mail.
Jenner and Tyga broke off their 20-month relationship last week. One Twitter user indicated that they had downloaded the illicit video before it was taken down.
Earlier this month, Tyga's sex tape with Blac Chyna was reportedly distributed to porn companies by a third party. If Tyga was instrumental in the posting of his sex tape with Jenner to his official website, he will fall at the mercy of California's new revenge porn laws.