The User Registration & Membership plugin for WordPress is vulnerable to Arbitrary Shortcode…

Why it is Yellow

• CVSS 8.1 high

References

• https://plugins.trac.wordpress.org/browser/user-registration/tags/5.2.8/includes/class-ur-smart-tags.php#L474
• https://plugins.trac.wordpress.org/browser/user-registration/tags/5.2.8/includes/class-ur-smart-tags.php#L475
• https://plugins.trac.wordpress.org/browser/user-registration/tags/5.2.8/modules/content-restriction/class-urcr-frontend.php#L1383
• https://plugins.trac.wordpress.org/browser/user-registration/tags/5.2.8/modules/content-restriction/functions-urcr-core.php#L693
• https://plugins.trac.wordpress.org/changeset/3741339/user-registration/trunk/includes/class-ur-smart-tags.php
• https://www.wordfence.com/threat-intel/vulnerabilities/id/ec317df9-c7ef-49a3-9818-903dfe4bdd03?source=cve

Original description

The User Registration & Membership plugin for WordPress is vulnerable to Arbitrary Shortcode Execution in versions up to, and including, 5.2.8 This is due to insufficient input sanitization in the 'referrer_url' branch of UR_Smart_Tags::process(), where the attacker-controlled HTTP_REFERER header is only passed through sanitize_text_field() — which does not strip WordPress shortcode delimiters — before being substituted into a Content Restriction message that is subsequently executed via apply_shortcodes()/do_shortcode(). This makes it possible for unauthenticated attackers to execute arbitrary registered shortcodes on any restricted page whose message uses the supported {{referrer_url}} smart tag.