Does anything like this exist?
You can find it here https://addons.mozilla.org/en-US/firefox/addon/10345/
Quote from the plugin page:
XMLHttpRequest, but also
eval, relevant JQuery methods, and might as well include image tags, script tags, XML tags, and any other tag that can retrieve a remote URI - CSS included.
However, if you have the option it would be much simpler to determine at runtime - simply attach a sniffer or proxy, and watch what happens.
Of course, you'd still have to make sure to trigger whatever conditions set it off, but still much simpler.
Simple would be to just grep for
XMLHttpRequest. But this is far from complete, because there are plenty of other ways to set up a HTTP request (e.g. by adding an image or script tag to the DOM). Additionally, a malicious user could use