I'm using a video hosting service that provides me with embed codes for the videos: something like this:
<iframe title="Part 1" width="640" height="360" allowTransparency="true" mozallowfullscreen webkitallowfullscreen allowfullscreen style="background-color:transparent;" frameBorder="0" src="https://app.vidgrid.com/embed/--video-id--"></iframe>
This works totally fine if embedded by a contributor on a SharePoint page (clicking "Add A Page > insert > Embed Code") because I have added the video's domain (app.vidgrid.com) to the HTML Field Security allowed list. But. We have a Video Library ("Libraries > Training Video Library > Add > Video") which also allows video iframes, but the contributor sees this error (works for me, as an admin):
My guess is, SharePoint isn't using the HTML Field Security allowed domain list for this video embed piece. Is there any hope? :D Or does everyone just need to add a full page for each video, or download the video as an MP4 and re-upload it to sharepoint (works but clunky).