GitLab

I noticed that this command

for x in find . -type f ; do grep -l '.onion' $x ; done

run from

/Applications/TorBrowser_en-US.app/Library/Application Support/Firefox/Profiles/profile

indicates that the urls of several sites I had visited had been saved in places.sqlite and in several bookmark backup files. Deleting places* didn't remove them, only that plus deleting all bookmark backups did the trick.