@pszufe, please see the following code.
devel@hpz4:~$ grep -inr "5c67c38e-c187-11e8-2be6-e3a6a3a5610f" ~
Binary file /home/devel/.mozilla/firefox/rtp7pfh3.default/favicons.sqlite-wal matches
Binary file /home/devel/.mozilla/firefox/rtp7pfh3.default/sessionstore-backups/recovery.baklz4 matches
Binary file /home/devel/.mozilla/firefox/rtp7pfh3.default/sessionstore-backups/recovery.jsonlz4 matches
Binary file /home/devel/.mozilla/firefox/rtp7pfh3.default/places.sqlite matches
Binary file /home/devel/.mozilla/firefox/rtp7pfh3.default/places.sqlite-wal matches
Binary file /home/devel/.mozilla/firefox/rtp7pfh3.default/favicons.sqlite matches