update browser

It appears you are running the old EOL macOS 10.11 and Firefox 78.15.0esr is the most current Firefox version you can run. https://support.mozilla.org/en-US/kb/firefox-mac-osx-users-esr Firefox 79.0 to 115.0 ESR requires macOS 10.12, 10.13, 10.14 to run while Firefox 116.0 and later requires macOS 10.16 (ten.fifteen) or later to run. https://support.mozilla.org/en-US/kb/firefox-users-macos-1012-1013-1014-moving-to-extended-support So unless you can update your macOS to 10.12 or later you not going to be able to run a more current Firefox version.