An extension isn't needed for that. Make it click-to-play ("Let me choose when to run plugin content") and then you can add any site you want to the exceptions

An extension isn't needed for that. Make it click-to-play ("Let me choose when to run plugin content") and then you can add any site you want to the exceptions list. An icon displays in the address bar when a plugin is on the page, click it and you can easily add the site to your exceptions list.