Main security concerns in allowing users embed video

Question

I wanna allow users to embed videos freely in the application in developing, but do not want to expose then and the application to malicious uses.

With that in mind, what are the main security concerns (XSS, etc) in allowing users to embed videos from external sources, like YouTube, Vimeo, etc. In which way this exploits could be used? What kind of sanitization you guys recommend to apply, before accepting/displaying an embed video?

Answer 1

Well once you allow a flash app to be on your site, it could do any number of things on the client that you wont have control over, especially since you can execute JavaScript with flash (with limitations). Best is to use a whitelist, and only allow users to embed videos from places you trust.