The Funnel Builder by CartFlows – Create High Converting Sales Funnels For WordPress plugin before 1.6.13 did not sanitise its facebook_pixel_id and google_analytics_id settings, allowing high privilege users to set XSS payload in them, which will either be executed on pages generated by the plugin, or the whole website depending on the settings used.
The product does not neutralize or incorrectly neutralizes user-controllable input before it is placed in output that is used as a web page that is served to other users.