You have mixed active content in v122 of the web app. This will error out with a mixed content warning in Firefox 23 and up. Users can manually add an exception, but that ain't good.
Thank you for your feedback. The latest stable public release of Firefox is 21.0 and we never support or debug the app against future non-final releases of any browsers (so far, every reported issue with every future browser was not present after its final release). Nonetheless, if the issue will persist when Firefox 23 will become final, we'll take a look at it.