You are likely on the Beta channel due to using a Beta build at some point instead of Release and continuing since. Firefox 49.0 is currently on the Beta channel at build 49.0b3 (3rd Beta build). See https://support.mozilla.org/en-US/kb/firefox-osx The current Firefox 48.0 Released on Aug 2nd still works on OSX 10.6, 10.7, 10.8 however once Firefox 49.0 is released the Firefox 48.0 is EOL so in order to still get security updates for Firefox you can use the Firefox 45 ESR branch then or you can switch now. Firefox 49.0 and later will require Mac OSX 10.9 at minimum to run. ESR channel builds generally get eight updates as 45.8.0 esr will be out when Firefox 53.0 is released. The 45.8.0 esr will then be the last unless Mozilla extends support to help Mac OSX 10.6, 10.7, 10.8 users for a while longer. https://www.mozilla.org/firefox/organizations/all/