Class Input Validation Error Remote Yes Credit Ricardo Sanchez Vulnerable WP Mailster 1.5.4.0 WP Mailster is prone to a stored cross-site scripting vulnerability because it fails to sufficiently sanitize user-supplied data. An attacker may leverage this issue to execute arbitrary script code in the browser of an unsuspecting user in the context of the affected site. This may allow the attacker to steal cookie-based authentication credentials and to launch other attacks. To exploit this issue following steps: The XSS reflected because the value mes is not filter correctly: Demo Request: http://localhost//wordpress/wp-content/plugins/wp-mailster/view/subscription/unsubscribe2.php?mes= </script>"><script>alert("XSS")</script>