When you are using Firefox and you navigate to Facebook, the browser is still on. It is still running on your computer. What that means is that potentially Firefox can know what you are doing on Facebook and then could potentially provide that information to us. Again, I say “potentially”, because that is not what we do. We very purposefully do not do that. We don't feel that this is the appropriate role for the browser. That is why we have a set of policies in place to govern the data collection that we have—exactly what Firefox gets to know about your activity on Facebook, and what data Firefox, the software running on your device, actually tells Mozilla.
As I said, although potentially any browser can monitor your activity and then disclose that activity to the company that makes the browser, that is not the position we are in or want to be in. We do not want to know about your activity on Facebook.