GTM4WP <= 1.22.3 - Unauthenticated Stored Cross-Site Scripting via WooCommerce Billing Fields

The GTM4WP – A Google Tag Manager (GTM) plugin for WordPress plugin for WordPress is vulnerable to Stored Cross-Site Scripting via WooCommerce Billing Fields in all versions up to, and including, 1.22.3 due to insufficient input sanitization and output escaping. This makes it possible for unauthenticated attackers to inject arbitrary web scripts in pages that will execute whenever a user accesses an injected page. This requires the GTM4WP WooCommerce order data integration option (GTM4WP_OPTION_INTEGRATE_WCORDERDATA) to be enabled, and is exploited by placing a guest checkout order with a JavaScript payload in a WooCommerce billing field such as the billing first name.