After updating to 4.7.10 we're finding that YouTube embeds are failing, showing a blank box. Digging into the elements, the src is being set with "data-embed-src", if I change it to just "src" the iframe works. In one example, I used the wysiwyg editor to manually insert an iframe as follows:
<iframe allowfullscreen="" frameborder="0" id="UIDREMOVED" name="fitvid0" src="https://www.youtube.com/embed/example?rel=0&showinfo=0&color=white"></iframe>
As you can see the source is defined with "src". This is correct and works.
However when the page loads, something is changing that tag to "data-embed-src":
<iframe allowfullscreen="" id="UIDREMOVED" name="fitvid0" src="https://www.example.com/applications/core/interface/index.html" data-embed-src="https://www.youtube.com/embed/example?rel=0&showinfo=0&color=white" frameborder="0"></iframe>
Lazy Loading is turned off in the Admin CP. What is changing that embed link on page load? If I examine the source of the post by bringing up the wysiwyg editor for the post it shows the correct, first version, but it's modified on page load.