You might have heard the news that future versions of Firefox will run the browser UI separately from web content. This is called Multi-process Firefox (also “Electrolysis” or “e10s”), and it is scheduled for release in the first quarter of 2016.

If your add-on code accesses web content directly, using an overlay extension, a bootstrapped extension, or low-level SDK APIs like window/utils or tabs/utils, then you will probably be affected.

To minimize the impact on users of your add-ons, we are urging you to test your add-ons for compatibility. You can find documentation on how to make them compatible here.

Starting Nov. 24, 2015, we are available to assist you every Tuesday in the #addons channel at irc.mozilla.org. Click here to see the schedule. Whether you need help testing or making your add-ons compatible, we’re here to help!

https://blog.mozilla.org/addons/2015/11/23/test-your-add-ons-for-multi-process-firefox-compatibility/