You said you removed the site from history but did you try cor-el's suggestion in [https://support.mozilla.org/en-US/questions/1228377/ this thread] where they suggested the user "Forget this website" to completely remove any data that might be associated with it? per cor-el: <blockquote> You can remove all data stored in Firefox from a specific domain via "Forget About This Site" in the right-click context menu of an history entry ("History -> Show All History" or "View -> Sidebar -> History"). Using "Forget About This Site" will remove all data stored in Firefox from this domain like history and cookies and passwords and exceptions and cache, so be cautious. If you have a password or other data from that domain that you do not want to lose then make sure to backup this data or make a note. You can't recover from this 'forget' unless you have a backup of involved files. If you revisit a 'forgotten' website then data from that website will be saved once again. https://support.mozilla.org/en-US/kb/delete-browsing-search-download-history-firefox </blockquote>