Exercise due caution with your data before doing these steps. Take a data backup first. In order to completely remove Firefox from Ubuntu Linux, open a terminal window and enter the following:
Delete the application
$ sudo apt-get purge firefox* <enter>
Remove the folders
$ sudo rm -Rf /etc/firefox <enter>
$ sudo rm -Rf /usr/lib/firefox* <enter>
$ cd /opt <enter>
$ sudo rm -rf firefox* <enter>
$ cd /usr/local/bin <enter>
$ sudo rm -rf firefox* <enter>
$ cd ~ <enter>
$ rm -rf .mozilla <enter>
$ rm -rf .cache/mozilla/firefox <enter>
$ sudo rm -rf /usr/lib/firefox/ <enter>
$ sudo rm -rf /usr/lib/firefox-addons <enter>
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