Links loaded as iframes in wordpress post

I noticed that links are loaded as iframes when viewed from frontend of site. FOr example I inserted this link:
https://developer.www.ads-software.com/reference/functions/wp_insert_post/
and on the frontend, this is the code showing when I inspect using firebug

<blockquote style="display: none;" data-secret="mfnLLDcIqY" class="wp-embedded-content">
	<p><a href="https://developer.www.ads-software.com/reference/functions/wp_insert_post/">wp_insert_post()</a></p>
</blockquote>
<p>
	<iframe class="wp-embedded-content" sandbox="allow-scripts" security="restricted" src="https://developer.www.ads-software.com/reference/functions/wp_insert_post/embed/#?secret=mfnLLDcIqY" data-secret="mfnLLDcIqY" title="“wp_insert_post()” — WordPress Developer Resources" marginwidth="0" marginheight="0" scrolling="no" frameborder="0" height="200" width="600">
	</iframe>
</p>

You can view this at this url at end of post:

https://www.kobopulse.com/index.php/2016/06/01/change-wordpress-post-titles-to-title-case-without-a-plugin/

What is responsible for this?

This is a big concern as my site is a multiauthor public site.