Hi nadjaho, That shouldn't happen. I've been on mac since 2007 and never lost Firefox data when updating the OS. If Firefox starts up after an update without your bookmarks and other settings, check whether your data is available in a different [[Profiles - Where Firefox stores your bookmarks, passwords and other user data|profile]]: Inside Firefox, type or paste '''about:profiles''' in the address bar and press Enter/Return to load it. The [[Use the Profile Manager to create and remove Firefox profiles#w_manage-profiles-when-firefox-is-open|About Profiles page]] will open. This page should list at least one profile and could list many. The profile that Firefox is currently using will show:<br> '''This is the profile in use and it cannot be deleted.''' ''Please do not delete anything here; don't use any Remove buttons.'' Do you have another profile named '''default''' or default-''longnumber'' listed on this page? If so, you can check whether it is the one you were using recently by clicking its '''Launch profile in new browser''' button. If it isn't what you want, simply close that new window. If it IS what you want, click the '''Set as default profile''' button for that profile on the about:profiles page. Firefox will use it automatically at the next startup. For more information see [[Recover user data missing after Firefox update]]. '''Note:''' If your bookmarks are not available in another Firefox profile, see [[Recover lost or missing Bookmarks]] for other solutions.

Hi Chris Ilias, thank you for your detailed reply, unfortuately it was not successful. All my mozilla files are dated and time to the when the upgrade was processed. This is strange as my other browsers retained their informatin. im not sure if its because I am using mozilla firefox developer mode?