CVE-2026-6431: WordPress User Profile Builder XSS Vulnerability

CVE-2026-6431 Overview

CVE-2026-6431 is a Stored Cross-Site Scripting (XSS) vulnerability [CWE-79] in the User Profile Builder plugin for WordPress. The flaw affects all versions up to and including 3.15.7. It resides in the handling of the Biographical Info meta field, where the plugin fails to properly sanitize input and escape output. Unauthenticated attackers can inject arbitrary JavaScript that executes in the browser of any user who views an affected page. The plugin, marketed as "Beautiful User Registration Forms, User Profiles & User Role Editor," is widely deployed on WordPress sites that expose public registration or profile pages.

Critical Impact
Unauthenticated attackers can inject persistent JavaScript that executes against site visitors and administrators, enabling session theft, forced administrative actions, and further site compromise.

Affected Products

User Profile Builder – Beautiful User Registration Forms, User Profiles & User Role Editor plugin for WordPress
All versions up to and including 3.15.7
WordPress sites exposing registration or profile forms that include the Biographical Info field

Discovery Timeline

2026-09-07 - CVE-2026-6431 published to the National Vulnerability Database
2026-09-09 - Last updated in NVD database

Technical Details for CVE-2026-6431

Vulnerability Analysis

The vulnerability is a stored XSS flaw in the plugin's front-end form processing and email confirmation workflow. When a user submits registration or profile data, the Biographical Info meta field is stored without adequate sanitization. On rendering, the value is echoed to the page without proper output escaping. Because the injection point is reached through the public registration form, no authentication is required to plant the payload.

Stored payloads execute in the context of the site's origin whenever a user, including administrators reviewing new registrations, accesses a page that displays the biographical field. This allows attackers to steal session cookies, perform actions on behalf of authenticated users, and pivot to full site takeover by targeting privileged accounts.

Root Cause

The root cause is insufficient input sanitization and missing output escaping in the plugin's form builder and email confirmation code paths. Referenced source lines in front-end/class-formbuilder.php (line 743) and features/email-confirmation/class-email-confirmation.php (line 95) handle the meta field value without applying WordPress escaping functions such as esc_html() or wp_kses(). Fix commit changeset 3511465 addresses the missing controls.

Attack Vector

An unauthenticated attacker submits a registration or profile update request containing a JavaScript payload in the Biographical Info field. The payload is stored in the WordPress user meta table. When any user, including an administrator, accesses a page that renders the affected profile data, the script executes in the browser under the site's origin. See the Wordfence Vulnerability Report for additional context.

// No verified exploit code is published for CVE-2026-6431.
// Refer to the Wordfence advisory and WordPress plugin changeset for technical details.

Detection Methods for CVE-2026-6431

Indicators of Compromise

Registration or profile update requests containing HTML or JavaScript syntax (<script, onerror=, onload=) in the description or biographical field
New or existing WordPress user records with meta key description containing script tags or event handlers
Unexpected outbound requests from browser sessions of administrators after visiting user profile or user list pages
Creation of new administrative WordPress accounts shortly after visits to user profile pages

Detection Strategies

Query the WordPress usermeta table for meta_key = 'description' values containing HTML tags or JavaScript event handlers
Inspect web server access logs for POST requests to wp-admin/profile.php, wp-login.php?action=register, or Profile Builder form endpoints with encoded script payloads
Deploy a Web Application Firewall (WAF) rule to flag XSS patterns targeting Profile Builder form fields
Review any recent installations or updates of the User Profile Builder plugin against version 3.15.7 or earlier

Monitoring Recommendations

Enable audit logging for WordPress user creation, role changes, and profile edits
Alert on new administrator account creation and on privileged user actions performed shortly after profile page views
Monitor plugin file integrity for the User Profile Builder directory to identify tampering or backdoor insertion
Correlate registration form submissions with subsequent administrative browser sessions using centralized log analytics

How to Mitigate CVE-2026-6431

Immediate Actions Required

Update the User Profile Builder plugin to the version that includes changeset 3511465 (later than 3.15.7) as soon as a fixed release is available
Audit all WordPress user records for stored payloads in the Biographical Info field and remove injected content
Rotate credentials and invalidate active sessions for administrators who may have viewed compromised profile pages
Review the site for unauthorized administrative accounts, new plugins, or modified theme files

Patch Information

The vendor addressed the issue in WordPress plugin Changeset #3511465. Site operators should upgrade to the first plugin release that incorporates this changeset. Reference source for the vulnerable logic is available in the WordPress Form Builder Code and WordPress Email Confirmation Code.

Workarounds

Temporarily disable the User Profile Builder plugin until the patched version is deployed
Remove or hide the Biographical Info field from public registration and profile forms
Deploy a WAF rule to block requests containing HTML or JavaScript tokens in Profile Builder form parameters
Restrict access to the WordPress registration page using IP allowlists or CAPTCHA controls to reduce exposure to unauthenticated attackers

bash

# Example WP-CLI query to identify potentially injected biographical entries
wp db query "SELECT user_id, meta_value FROM wp_usermeta \
  WHERE meta_key='description' \
  AND (meta_value LIKE '%<script%' \
       OR meta_value LIKE '%onerror=%' \
       OR meta_value LIKE '%onload=%');"