How can Yelp and Netflix see my Facebook stuff (Cross domain cookie access)?

I thought nothing cross domain can be done. Then how come when I goto Netflix, it tells me which of my friends have liked it.

In fact I've gone to some random blog, and it was showcasing some product I had liked, and it told me that I had liked the product. So, basically it was able to read my Facebook cookie or something.

What's the deal here?

Are they making XmlHttpRequest calls to Facebook? But how can they, it's denied in modern brows开发者_如何学Goers

It's probably an iframe or image loaded from the facebook domain, which can tell whether you're logged in. Don't worry, the blog page can't look inside or touch your private information within.