How to add an attribute to CkEditor 4.x iframe tag Does anyone know of a clean way to add an attribute to an iframe tag, or to add an equivalent parameter to the src attribute? Here is what I am trying to do:

I am using the iframe wysiwyg button in Ckeditor to allow users to paste in a video url from YouTube. The problem is, the mega menu dropdown shows up behind the video. To fix this, the iframe tag for the video either needs to have the attribute wmode="transparent added to it, or the actual src url needs to have the parameter &amp;wmode=transparent appended.

Ideally, this would be enforced and not asked of the user. Has anyone dealt with this and implemented a solution? If so, please let me know what you did. Thanks!
As a quick and dirty work-around, I used jquery to add a parameter to the url (which always has at least one parameter already, thus the ampersand).

$('iframe').each(function() {
      $(this).attr("src", $(this).attr("src") + '&amp;wmode=transparent')
  });

But I want to later refine this to only target urls starting with https://www.youtube.com at the very least and use an attribute instead of a parameter. If anyone can suggest the code for that based on what's above, that would be appreciated. If not, I'll eventually update this post with that code when I have more time to figure it out. Thanks.