If you want to scroll the screen down you get a pop up, that pop up will instruct you to do something- which will install some back crap on your device.
Oh and those pop ups happen for clicking the play button (it'll pop up at least three times before it'll start), pausing the screen, OH and for after you click the scroll bar pop up away and want to stop it auto-scrolling with your mouse and click again that gives you a SECOND pop up!
So if you're going to watch- lots and LOTS of pop ups and make sure it doesn't download anything and you have a good anti-spyware and anti-malware programs!