Please check the version using

Menu {3bar icon) => Help {(?) icon) => about firefox

That should show your version and it should also trigger an update if you are not up to date. The latest version is Fx53.0.2 See

• Release notes: https://www.mozilla.org/firefox/53.0.2/releasenotes/
• Security notes: https://www.mozilla.org/security/known-vulnerabilities/firefox/
• Help article Update Firefox to the latest release

There are additional steps that may be needed if the updates got mixed up and not installed properly because of the interrupted update.

Note that on Mac it is: "Firefox > About Firefox". See also the "Help -> Troubleshooting Information" page (about:support).

If there a problem with updating or with the permissions then best is to download the full version and trash the currently installed Firefox application to do a clean reinstall.

Download a new copy of the Firefox application and save the Disk Image file to the desktop

• Firefox 53.0.2: *https://www.mozilla.org/en-US/firefox/all/

• trash the currently installed Firefox application (open the Applications folder in the Finder and drag the Firefox application to the Trash) to do a clean reinstall
• install the new version that you have downloaded
• https://support.mozilla.org/en-US/kb/Installing+Firefox+on+Mac

Your personal data like bookmarks is stored in the Firefox profile folder, so you won't lose personal data when you uninstall and reinstall or update Firefox, but make sure NOT to remove personal data when you uninstall Firefox as that will remove all Firefox profile folders and you lose your personal data.

• http://kb.mozillazine.org/Profile_folder_-_Firefox