Mozilla’s legacy Firefox ESR v115.x for Win 7 and Win 8.x will soon reach official end of support next month with the final 19-Aug-2025 release of Firefox ESR v115.27.0.
Affected users might be interested in reading Alex5723’s 16-Jul-2025 topic r3dfox Firefox based web browser for Windows Vista ,7! and 8 in the AskWoody forum. The r3dfox browsers are a fork of modern Firefox browsers that have been modified by K4sum1 to work with Win Vista, Win 7, and Win 8.x. I haven’t tried r3dfox myself but it appears to be gaining popularity amongst users with older Windows operating systems who would like to continue using a Firefox browser that incorporates recent security patches.
As of today K4sum1 has posted modified installers for Firefox ESR v128.12.0 (rel. 24-Jun-2025) and Firefox v140.0.4 (rel. 08-Jul-2025) on their alternate SourceForge download page <here> that should run on most Win Vista and higher machines.
Dell Inspiron 15 5584 * 64-bit Win 10 Pro v22H2 build 19045.6216 * Firefox v142.0.0 * Microsoft Defender v4.18.25070.5-1.1.25070.4 * Malwarebytes Premium v5.3.6.205-138.0.5346 * Macrium Reflect Free v8.0.7783