I recently developed a cross-browser extension using crossrider.com, it seemed like a reasonable choice of "framework" with multiple recommendations in blogs, etc.
The trouble is crossrider also run an ad network and it seems they're sending browser meta data to that network from all their browser plugins. Sophos are blocking their use (although it is possible to add an exception). Chrome is now also blocking the installation of staging versions of your extension during development.
I would love to hear from crossrider but haven't had a reply to my emails.
So my question is can anyone recommend an alternative framework for cross-browser extension development.