Been sketching on an editor which will work sort-of the same way as the collaborative example, but not real-time. However, rather than working on an instance and adding steps as the collaborative example, I was thinking of serialising the document as a JSON blob, and send that between clients. This breaks for concurrent edits, but that has been thought of.
One such example I can think of would be: https://www.owasp.org/index.php/Script_in_IMG_tags
What do you think?