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

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.

Source published

17 Oct 2026 03:43:31 UTC

Source modified

18 Oct 2026 11:22:46 UTC

Observed here

23 Oct 2026 15:48:27 UTC

Source terms

CVE Program Terms of Use

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CVSS 3.1 · 8.1 CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:N