When embedding video to a knowledge article, the message "This plugin is not supported" appears after the upload is complete.

The product documentation states that .mov, .avi, and .swf. files are supported (although only .swf files can be uploaded), however, regardless of the format, the video will not embed after saving the knowledge base article.

1. Open a knowledge base article.
2. In the Text field toolbar, click the insert/edit video button .
3. Insert a .mov file or .avi file.
4. Click Upload.
   When upload is complete, the message This plugin is not supported appears. If you click OK, the video in embedded, but not playable.
5. View the knowledge base article.
   The video does not stay with the article.
   
   

This problem has been fixed in Jakarta and Kingston, however, further steps to disable the HTML Sanitizer are still required, please refer to the documentation below:

Embed videos in HTML fields