What is the difference between open() and window.open() in Firefox?

Question

In answering my question Pumbaa80 found a difference between calling open() and window.open(), try the following examples in Firefox

Answer 1

This is indeed very strange. It looks like The onclick handler when added as an attribute has some context with a wrapped open function that differs from window.open:

http://jsfiddle.net/aFujb/

This happens in latest Firefox, Safari and Chrome. I can't find any explanation or bug report for either browser.

I tried to find out what's happening in Firefox's source code, but quite honestly it's too much for me atm. Looks there's two different window.open implementations called nsGlobalWindow::Open and nsGlobalWindow::OpenJS, but I'm not sure whether this has something to do with the question.