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.
https://plugins.trac.wordpress.org/browser/yaymail/trunk/src/Ajax.php#L183
https://plugins.trac.wordpress.org/browser/yaymail/tags/4.3.2/src/Ajax.php#L183