Except where noted, everything here applies to both Firefox 99 and the Firefox 91.8 ESR.
- If you specified a value for install_sources in ExtensionSettings, add-ons could still be installed from addons.mozilla.org. This was fixed for Firefox 99 in bug 1735806. Because the fix involved localization, it will not be available in an ESR until the next major ESR update (102).
- When configuring Outlook Web Access, some fields didn't work properly. This was fixed in bug 1736570 and is now fixed in the ESR.
Firefox 100 will be released on May 3, 2022. We've created a blog post that has more detail:
We strongly encourage taking some time to test your internal applications to make sure they work properly with Firefox 100.
Similar to Chrome, we will be providing a preference (network.http.useragent.forceVersion) that can be set using the Preferences policy if for some reason you need to keep the version below 100.