The website, which describes itself as showcasing "explosive celebrity gossip from Islamic extremists" posted what it is calling a sex tape of Penn, 25, the model and actress daughter of Sean Penn and Robin Wright, reported Metro online.
The site also includes topless photos of Penn.
Cassidy also found herself the victim of an illegal hack when the site posted a series of pictures of the "Arrow" star.
Other celebrities who have recently had nude photos or videos hacked include actresses Rhona Mitra, Amanda Seyfried and Mischa Barton.