Virus from watching movies

So theres this app called Web video caster which allows you to watch movies from you phone on your tv. The app uses another browser not safari or google and you have to be on the movie site in your phone during the whole time. Is there any risk from using it on iphone since you still have to be on the movie site and the apps browser? The app blocks all pop up ads but still worried if theres a risk for a virus?