The latest Firefox release is 21.0 If there are problems with updating or with the permanently then best is to download the full version and trash the currently installed version to do a clean install of the new version. Download a new copy of the Firefox program and save the disk image (dmg) file to the desktop *Firefox 21.0: http://www.mozilla.org/en-US/firefox/all.html *Trash the current Firefox application (e.g. open the Applications folder in the Finder and drag the Firefox application to the Trash) to do a clean (re-)install *Install the new version that you have downloaded *https://support.mozilla.org/kb/Installing+Firefox+on+Mac Your personal data is stored elsewhere in the Firefox profile folder, so you won't lose your bookmarks and other personal data when you uninstall and (re)install Firefox. *http://kb.mozillazine.org/Profile_folder_-_Firefox

You can find [https://support.mozilla.org/en-US/kb/find-what-version-firefox-you-are-using what version of Firefox you are using] here