If you attempt to use Video/Audio optional Attributes in the CMS HTML input box that are boolean types that do not use the "=" expression, the CMS validation will incorrectly prompt a save error and stop the user from using this kind of HTML functionality. Some examples are the attributes autoplay, controls, loop, and muted.

1. Go to the legacy CMS application
2. Create a new HTML template
3. Insert a valid HTML tag that contains the autoplay attribute, for example:

<video controls loop> <source src="movie.mp4" type="video/mp4"> <source src="movie.ogg" type="video/ogg">   Your browser does not support the video tag. </video>

4. An error will be prompted to the user.

Use a javascript with the HTMLMediaElement.loop property instead, generating the same end effect.