Firefox 22 changes embed tag behavior (at least with Quicktime plugin for audio playback)

Firefox 22 does not support an embed tag with a "hidden" attribute. Even if the "hidden" attribute is set to false (hidden="false"). This worked fine in Firefox 21 and all previous versions.

This is broken in Firefox 22:

<embed src="my_audio.wav" autostart="true" loop="false" hidden="true"></embed>

This works though!

<style>
.x-hidden {
  position: absolute;
  left: -999em;
}
</style>

<embed src="my_audio.wav" autostart="true" loop="false" class="x-hidden"></embed>

(By the way, Ext 3 defines a similar x-hidden class that is often used for their controls if you want to start them hidden, since they do not play well with initializing controls in a hidden div.)