The Salon booking system plugin for WordPress is vulnerable to unauthorized access and modification of data due to a missing capability check on several functions hooked into admin_init in all versions up to, and including, 9.9. This makes it possible for authenticated attackers with subscriber access or higher to modify plugin settings and view discount codes intended for other users.
https://plugins.trac.wordpress.org/browser/salon-booking-system/trunk/src/SLN/Admin/Tools.php#L231
https://plugins.trac.wordpress.org/browser/salon-booking-system/trunk/src/SLN/Admin/Tools.php#L16
https://plugins.trac.wordpress.org/browser/salon-booking-system/trunk/src/SLN/Admin/Tools.php#L12