I was trying out the new WebExtensions.
I am on Firefox 42.0 release version which has some support for WebExtensions.
I was testing out https://github.com/mdn/webextensions-examples/tree/master/beastify but the JavaScript does not work.
Am I missing something or the JS support is not present in FF42.0?
That isn’t much of a bug report 
What does it actually do?
First time use in firefox 42.0 ubuntu the popup comes up with a menu of beasts.
Clicking a beast shows visual feedback, but the popup stays and no beast loads in the active tab.
On subsequent attempts the popup shows a grey background, no menu entries.
The extension works fine for me in firefox 44 and 45 on ubuntu.
Thank you @anaran
This isn’t a bug report per se. I was trying out the WebEx concept and run into a dead-end.
On Windows FF42.0, the popup comes up with a menu of beasts.
Clicking the beast does nothing and no errors on the console.
I have tried a few sample WebEx addons and none of them run their JS
I dont use not-release versions of FF.