The embed player is probably trying to invoked autoplay (either setting it to true or false)
And firefox is reacting to that.
it’s not in your project, but the attribute is attempted to be used/set by the iframe.
You could be running and outdated version of Firefox that doesn’t supported the directive?
A quick google returns this https://bugzilla.mozilla.org/show_bug.cgi?id=1390801 I don’t know the current status of Firefox development.
And this dev tools warning is safe to ignore, unless you are trying to make VOD’s auto play, and they are not.