The Super Progressive Web Apps plugin for WordPress is vulnerable to Stored Cross-Site Scripting via the superpwa_settings[offline_message_txt] setting in all versions up to, and including, 2.2.43. This is due to insufficient input sanitization and output escaping. The offline message value is stored without sanitization, passed to the frontend via wp_localize_script() without escaping, and rendered using innerHTML in the JavaScript snackbar component. This makes it possible for authenticated attackers, with Administrator-level access and above, to inject arbitrary web scripts in pages that will execute whenever a user triggers the offline snackbar.