By dragging this link to your bookmarks toolbar and then clicking it to see an alert of the contents of a remote HTML file (something which sites can normally not do unless the site is hosted on their own domain), bearing in mind again, that if you grant AsYouWish privileges to the site on which the code is hosted (e.g., Github), whether as a normal page or a bookmarklet, the site will be able to invoke those privileges (including if the site were found to be open to exploits).

This is the code above in a readable format:

if (typeof AsYouWish === 'undefined') {
    alert("You do not appear to have AsYouWish installed. Redirecting to Github...");
    return window.location = 'https://github.com/brettz9/asyouwish/';
}
var require = AsYouWish.requestPrivs;
var xhr = require('sdk/net/xhr');
var x = new xhr.XMLHttpRequest();
x.open('GET', 'http://mozilla.org/', false);
x.send(null);
alert(x.responseText);