title: Why am I Blocked from accessing a same-origin frame using "window.opener"?
body: <p>I'm using Google Chrome and Adblock Plus.</p>
  
  <p>Firstly, I opened <code>https://www.google.com.sg/</code> with Chrome and then open a console and input <code>window.open("https://www.google.com.sg/")</code> in the console. </p>
  
  <p>Then a new window will appear. I input <code>window.opener.document</code> in the new window's console, but it throws an error:</p>
  
  <blockquote>
    <p>"Blocked a frame with origin "<a href="https://www.google.com.sg" rel="nofollow">https://www.google.com.sg</a>" from
    accessing a cross-origin frame."</p>
  </blockquote>
  
  <p>I am quite confused because I'm using same-origin frame (Both window are from the same origin "<a href="https://www.google.com.sg" rel="nofollow">https://www.google.com.sg</a>") instead of cross-origin frame.. Why does the brower still complains about the Security Error?</p>