It's an Add-on (Extension) that you, or someone, installed in your Firefox. Add-ons (Extensions) do not install themselves and this item is not included with the standard Firefox installation. *Short description here --> https://addons.mozilla.org/en-US/firefox/addon/mozrepl/ *More detail here --> https://github.com/bard/mozrepl/wiki/ *If you want to uninstall or remove the Add-on **https://support.mozilla.org/en-US/kb/disable-or-remove-add-ons **https://support.mozilla.org/en-US/kb/Cannot%20uninstall%20an%20add-on '''If this reply solves your problem, please click "Solved It" next to this reply when <u>signed-in</u> to the forum.'''