title: React iframe sandbox don't allow anything
body: <p>I have a requirement to use iframe sandbox in React application. In which, I don't want to allow anything and restrict everything.</p>
  
  <p>So when I am passing sandbox as blank, something like:-</p>
  
  <pre><code>&lt;iframe
    frameBorder="0"
    ref={(container) =&gt; { this.container[index] = container; }}
    srcDoc={thread.body}
    sandbox
  /&gt;
  </code></pre>
  
  <p>I am getting this - "Warning: Received <code>true</code> for a non-boolean attribute <code>sandbox</code>."</p>
  
  <p>react: "^16.5.2"</p>