User Registration & Membership <= 5.2.8 - Authenticated (Subscriber+) Arbitrary Shortcode Execution via Referer Header via 'referrer_url' Smart Tag

Summary

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.

Timeline

1. Oct 17, 2026, 3:43 AM UTCCVE published
2. Oct 18, 2026, 11:07 AM UTCCISA SSVC assessment

   Exploitation: none · Automatable: no · Technical impact: total

3. Oct 18, 2026, 11:22 AM UTCRecord last updated

Affected versions

• wpeverest User Registration & Membership – Free & Paid Memberships, Subscriptions, Content Restriction, User Profile, Custom User Registration & Login Builder

  through 5.2.8

References 6