Script player blocked by Content Security Policy for GitHub on Firefox

I tried to use this extension. On Firefox, I get this error:


Content Security Policy: The page’s settings blocked the loading of a resource at https://asciinema.org/a/Hr6o4z5O2AMEZKnTTPQenpOot/iframe? (“frame-src”).

I get that this isn’t really a problem with asciinema, but is there a way to work around it?