In Firefox 3.5.8, when I attempt an illegal cross-origin request, the "success" callback is still called. Firefox's response to an illegal cross-origin request is now to blank xhr.responseText and set xhr.status to zero, even though xhr.readyState === 4.

This should be reproducable by simply attempting a cross-origin request to a domain that does not support it, for example with the following code:

$.ajax({

url : "http://www.example.com/",

success : function() {

alert( "Oops!" );

}

});