 Template tags are not allowed.
    </template>
  </div>
</template>

<!-- Not descendant from a template, so mustache attribute values are OK -->
<p title="{{{allowed }}}"></p>
<p title="{{&allowed }}"></p>
<p title="{{>allowed }}"></p>

<!-- Inside a template, attribute value restrictions are relaxed. -->
<amp-audio src="https://example.com/audio" layout="fixed" autoplay="{{invalid}}">
<template type="amp-mustache">
<amp-audio src="https://example.com/audio" layout="fixed" autoplay="{{valid}}">
</template