FunnelKit < 3.15.0.6 - Reflected XSS via Divi Optin Form

The FunnelKit WordPress plugin before 3.15.0.6 does not escape a user-supplied parameter before reflecting it into the HTML response of one of its page-builder AJAX actions, allowing unauthenticated attackers to perform Reflected Cross-Site Scripting against logged-in users who open a crafted page. The affected action is only registered when the Divi /builder is active.