xmlhttprequest.js contains a nasty hack to emulate IE activex support:

// ActiveXObject emulation
if (!window.ActiveXObject && window.XMLHttpRequest) {
window.ActiveXObject = function(type) {
switch (type.toLowerCase()) {
case 'microsoft.xmlhttp':
case 'msxml2.xmlhttp':
return new XMLHttpRequest();
}
return null;
};
}

That's very bad since plugins can no longer rely on 'window.ActiveXObject' to check for activex support in the current browser.

This method is widely used when we try to embed a browser plugin (Flash Player for instance) to check of the browser should load the activex or the mozilla plugin.