The YayMail - WooCommerce Email Customizer plugin for WordPress is vulnerable to unauthorized plugin installation and activation due to missing capability checks on the 'yaymail_install_yaysmtp' AJAX action and `/yaymail/v1/addons/activate` REST endpoint in all versions up to, and including, 4.3.2. This makes it possible for authenticated attackers, with Shop Manager-level access and above, to install and activate the YaySMTP plugin.

The YayMail – WooCommerce Email Customizer plugin for WordPress is vulnerable to Stored Cross-Site Scripting via settings in all versions up to, and including, 4.3.2 due to insufficient input sanitization and output escaping. This makes it possible for authenticated attackers, with Shop Manager-level permissions and above, to inject arbitrary web scripts in pages that will execute whenever a user accesses an injected page. This only affects multi-site installations and installations where unfiltered_html has been disabled.

The YayMail – WooCommerce Email Customizer plugin for WordPress is vulnerable to unauthorized license key deletion due to a missing authorization check on the `/yaymail-license/v1/license/delete` REST endpoint in versions up to, and including, 4.3.2. This makes it possible for authenticated attackers, with Shop Manager-level access and above, to delete the plugin's license key via the '/yaymail-license/v1/license/delete' endpoint granted they can obtain the REST API nonce.

The YayMail – WooCommerce Email Customizer plugin for WordPress is vulnerable to unauthorized modification of data that can lead to privilege escalation due to a missing capability check on the `yaymail_import_state` AJAX action in all versions up to, and including, 4.3.2. This makes it possible for authenticated attackers, with Shop Manager-level access and above, to update arbitrary options on the WordPress site. This can be leveraged to update the default role for registration to administrator and enable user registration for attackers to gain administrative user access to a vulnerable site.