For the old eol macOS 10.9, 10.10, 10.11 the most current Firefox version you can run is Firefox 78.15.0esr which you appear to have. https://support.mozilla.org/en-US/kb/firefox-mac-osx-users-esr If you can update your macOS to 10.12 - 10.14 then you would be able to run the still getting updated Firefox 115 ESR currently at 115.31.0esr. https://support.mozilla.org/en-US/kb/firefox-users-macos-1012-1013-1014-moving-to-extended-support Firefox 116.0 and later requires macOS 10.15 (ten.fifteen) or later to run.