This is the embed code I got from Facebook

However, if I change the height inside the iframe tag to something smaller than 703, say set it to 300. The page inside the content isn't scrollable, even I changed the scrolling to yes

Check the Facebook page source, the overflow is set to hidden for the plugin class.

If I unset the overflow, the page can be scroll. But since it's an iframe embed, what can I do to unset the css in the child page which is hosted inside iframe? Thanks!