Is Firefox 78 Still Supported?
Firefox 78 is the last major release with support for macOS versions 10.9, 10.10 and 10.11. Users of these macOS versions will be supported through Firefox ESR 78. x for the coming year. You can read more about this here.
How long will Firefox ESR 78 be supported?
Special notes. Firefox 78 ESR is the last version of Firefox that supports Flash. The last version of that ESR will be 78.15, which is scheduled to be released on 2021-10-05. This means that Flash will officially be out of support on Firefox when Firefox 78 ESR reaches EOL on 2021-11-02.
Firefox | endoflife.date
On the menu bar, click the Firefox menu and select About Firefox. The About Firefox window will appear. The version number is listed underneath the Firefox name. Opening the About Firefox window will, by default, start an update check.
Find what version of Firefox you are using - Mozilla Support
What versions of Firefox are still supported?
There are only 2 currently updated and supported Released versions, Firefox 9.0. 1 and Firefox 3.6. 25.
Supported Versions | Firefox Support Forum | Mozilla Support