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.
References6
- plugins.trac.wordpress.org/browser/user-registration/tags/5.2.8…
- plugins.trac.wordpress.org/browser/user-registration/tags/5.2.8…
- plugins.trac.wordpress.org/browser/user-registration/tags/5.2.8…
- plugins.trac.wordpress.org/browser/user-registration/tags/5.2.8…
- plugins.trac.wordpress.org/changeset/3741339/user-registration/…
- www.wordfence.com/threat-intel/vulnerabilities/id/ec317df9-c7ef…
Metrics
- CVSS 3.1
-
8.1
HIGH
Score source: CNA
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:N - EPSS — exploit probability
- 0% percentile: 31 · as of 10 November 2026
- CWE
- CWE-94
Could this be exploited in your environment?
A patch closes the known hole. A penetration test shows what an attacker can still reach — with proof.