Strange iframe added into body tags called `rufous-sandbox`
It seems like it is added by the Twitter script. If you remove it the iframe will disappear.It sure looks like you have the Twitter plugin installed in some way or the other as you can see it says data-twttr-rendered="true" in the body tag.
If you remove the code - in my case the code below - it will disappear
<script type="text/javascript"> (function(){ var twitterWidgets = document.createElement('script'); twitterWidgets.type = 'text/javascript'; twitterWidgets.async = true; twitterWidgets.src = '//platform.twitter.com/widgets.js'; document.getElementsByTagName('head')[0].appendChild(twitterWidgets); })();</script>