I am running OS 10.11.6 but this problem happened prior to my upgrading from 10.9.6. When I do an upgrade to firefox (current is 66.0.3) I get a failure on the restart of firefox. It prompts me to download and reinstall from website. I got to www.mozilla.org and download the mac installation dmg. When I install and restart firefox through a long wait it launches. I then run FlashbackRemoval from F-Secure and it states it found malware. This has been happening for a long period of time. It happens only when I install an update for Firefox. I have tried to remove Firefox and reinstall but must not be getting all the files removed. Is there a way to uninstall ALL of firefox on a macOS and try and fresh reinstall