title: Cross-site XMLHttpRequest
body: <p>I want to provide a piece of Javascript code that will work on any website where it is included, but it always needs to get more data (or even modify data) on the server where the Javascript is hosted. I know that there are security restrictions in place for obvious reasons.</p>
  
  <p>Consider index.html hosted on xyz.com containing the following:</p>
  
  <pre><code>&lt;script type="text/javascript" src="http://abc.com/some.js"&gt;&lt;/script&gt;
  </code></pre>
  
  <p>Will some.js be able to use XMLHttpRequest to post data to abc.com? In other words, is abc.com implicitly trusted because we loaded Javascript from there?</p>