Mozilla releases Unbranded versions of Firefox for developers to test unsigned add-ons. When the extension signing announcement was made, Mozilla said it will release special builds for developers when the release and beta versions no longer allow them to disable extension signing by using a preference.
With Firefox 48 release, the time has finally come. The company has today released Unbranded Firefox builds for beta and release with the support for the setting to disable mandatory signature checks, and are available on the extension signing page for download.
Note: The Unbranded release build will be available on Aug 2 after Firefox 48 release. Update: Now available.
Firefox Unbranded builds
“With the release of Firefox 48, extension signing can no longer be disabled in the release and beta channel builds by using a preference. As outlined when extension signing was announced, we are publishing specialized builds that support this preference so developers can continue to test against the code that beta and release builds are generated from. These builds do not use Firefox branding, do not update automatically, and are available for the en-US locale only.” Mozilla’s Kev Needham said in a blog post published on Mozilla add-ons blog.
Advanced users may better stay away from testing these and stick to Nightly because, apart from not having Firefox branding –logo and name–, these builds also ‘do not update automatically and are available for the en-US locale only’.
Issue: Currently, Unbranded Beta builds downloaded and installed are automatically updated to branded Firefox builds. Mozilla is aware of this and working to fix it, you can follow this bug progress, interim the company posted a workaround on the extensions signing page for the developers who are testing can try.