title: Open.window() Document.referrer from HTTPS site to HTTP site empty
body: <p>Site1.com offers the possibility to open Site2.com in another window through a button. Site2.com checks document.referrer. As long as Site1.com and Site2.com are using HTTP everything works fine, and the referrer attribute contains the URL of Site1.com. </p>
  
  <p>If Site1.com runs with SSL (<a href="https://site1.com" rel="nofollow">https://site1.com</a>), but Site2.com doesn't, the referrer is suddenly empty.</p>
  
  <p>JS Client code on <a href="https://site1.com" rel="nofollow">https://site1.com</a></p>
  
  <pre><code>window.open("http://site2.com", "mySite2.com")
  </code></pre>
  
  <p>The Site2.com checks the referrer in the JS client code by: </p>
  
  <pre><code>document.referrer
  </code></pre>
  
  <p>Which turns out to be empty.</p>
  
  <p><strong>My Question</strong>:
  Is this a Javascript problem or an Nginx problem? Why is the referrer empty when using HTTPS on Site1.com ? </p>
  
  <p>Again, if both sites are using HTTP, everything works just fine. The referrer just doesn't get passed on the Site2.com is Site1.com is using HTTPS.</p>