Is it a separate program or an add-on?

Bookmark and use this; Download the Mozilla Search Reset https://addons.mozilla.org/en-US/firefox/addon/searchreset/

This add-on is very simple: on installation, it backs up and then resets your search preferences and home page to their default values, and then uninstalls itself. This affects the search bar, URL bar searches, and the home page.

You can check the home page setting.

• Options/Preferences -> General -> Startup: Home page
• https://support.mozilla.org/en-US/kb/how-to-set-the-home-page

Firefox supports multiple home pages separated by '|' (pipe) symbols.

See also:

• https://support.mozilla.org/en-US/kb/disable-or-remove-add-ons
• https://support.mozilla.org/en-US/kb/uninstalling-toolbars