Embedding external content in modern SharePoint Online (SPO) pages is a really easy task using Microsoft’s out of the box Embed webpart.
In the WebPart settings panel we can add the external content URL (such as a YouTube video) or by using the standard <iFrame> HTML tag:
In the event we want to add a reference to external content not allowed by default in SPO, we will need to add the domain URL in the “HTML Field Security” setting that can be found in the site settings page:
Once we browse that configuration page, we need simply to add the new domain / URL in case is not there yet.
We cover SharePoint Online in Chapter 9 for the Office 365 for IT Pros eBook.