What Is Causing Some Sites Are Embedded Within An Iframe in Google Chrome?

Some sites are served within an iframe (only) on Chrome.

Here's an example of the source code of Digg.com served within an Iframe:

<html class="gr__digg_com">
<head>
    <noscript>
        <meta http-equiv="refresh" content="0;URL=http://digg.com/"/>
    </noscript>
    <script type="text/javascript" src="http://ibnads.xl.co.id/ads-request?t=4&amp;j=2&amp;callback=iframe.jsonp454&amp;rnd=452&amp;a=http%3A%2F%2Fdigg.com%2F&amp;i=176791713"></script>
</head>
<body data-gr-c-s-loaded="true">
    <div id="container">
        <div id="top-banner"></div>
        <div id="middle">
            <div id="left-banner"></div>
            <div id="content">
                <iframe id="main-frame" frameborder="0" style="width: 1333px; border: 0px; height: 8200px;" src="http://digg.com/"></iframe>
            </div>
            <div id="right-banner"></div>
        </div>
        <div id="bottom-banner"></div>
    </div>      
    <script type="text/javascript">p={'t':'4', 'i':'176791713'};</script>
    <script src="http://ibnads.xl.co.id:8004/COMMON/js/if_low_20150915.min.js"></script>
</body>
<iframe allowtransparency="true" frameborder="0" id="abs-top-frame" src="chrome-extension://flliilndjeohchalpbbcdekjklbdgfkk/html/top.html?1457289833178#minimized" style="position: fixed !important; z-index: 2147483647 !important;overflow: hidden !important; top: 0px !important; left: 0px !important; right: 0px !important; width: 0px !important; height: 0px !important; max-height: none !important; min-height: 0px !important; margin: 0px auto !important; padding: 0px !important; border: 0px !important; display: none !important; background-color: transparent !important;"></iframe>
<span class="gr__tooltip"><span class="gr__tooltip-content"></span><i class="gr__tooltip-logo"></i><span class="gr__triangle"></span></span>
</html>

The actual Digg.com content is embedded within<iframe id="main-frame">.

This causes an ugly extra vertical scroll bar.

The URL in the address bar is still digg.com.

I tried to visit the sites (digg.com and some other sites) in Firefox, and they look fine.

I suspect that it's caused by a browser extension, but I don't know what it is.

Here are all browser extensions I have installed on Chrome:

Alexa Traffic Rank
Avira Browse Safety
Google Docs
Google Docs Offline
Google Mail Checker
Google Sheets
Google Slides
Grammarly
Instapaper
Wikiwand

Does anyone know why some sites are being served within an Iframe on Chrome?

What Is Causing Some Sites Are Embedded Within An Iframe in Google Chrome?

2 Answers