CVE-2026-1454: WordPress Contact Form Plugin XSS Flaw

CVE-2026-1454 Overview

The Responsive Contact Form Builder & Lead Generation Plugin for WordPress contains a Stored Cross-Site Scripting (XSS) vulnerability affecting all versions up to and including 2.0.1. The vulnerability exists in the form field submission handling functionality due to insufficient input sanitization in the lfb_lead_sanitize() function, which fails to sanitize certain field types. Combined with an overly permissive wp_kses() filter at output time that allows onclick attributes on anchor tags, this creates a significant attack vector.

This vulnerability enables unauthenticated attackers to inject arbitrary JavaScript code into lead form submissions. The malicious scripts execute whenever a WordPress administrator views the lead entries in the dashboard, potentially leading to session hijacking, account compromise, or further malicious actions performed with administrator privileges.

Critical Impact

Unauthenticated attackers can inject persistent malicious scripts that execute in the context of WordPress administrators, potentially leading to complete site compromise through admin session hijacking.

Affected Products

• Responsive Contact Form Builder & Lead Generation Plugin for WordPress versions ≤ 2.0.1
• WordPress installations utilizing the vulnerable plugin versions
• WordPress dashboards where administrators review lead form entries

Discovery Timeline

• 2026-03-11 - CVE-2026-1454 published to NVD
• 2026-03-11 - Last updated in NVD database

Technical Details for CVE-2026-1454

Vulnerability Analysis

This Stored XSS vulnerability (CWE-79) presents a network-accessible attack vector that requires no authentication or user interaction from the victim during the initial injection phase. The vulnerability's impact stems from a two-stage failure in the plugin's security controls.

The first failure occurs in the lfb_lead_sanitize() function located in inc/ajax-functions.php, which maintains a sanitization whitelist that omits certain form field types. When attackers submit form data through unprotected field types, malicious content bypasses the initial sanitization layer entirely.

The second failure manifests at output time in the inc/show-lead.php file, where an improperly configured wp_kses() filter allows dangerous attributes including onclick on anchor tags. This combination enables stored XSS payloads to persist in the database and execute when rendered in the WordPress admin dashboard.

Root Cause

The root cause is a combination of incomplete input sanitization and an overly permissive output encoding configuration. The lfb_lead_sanitize() function does not apply proper sanitization to all form field types, creating gaps in the input validation layer. Additionally, the wp_kses() filter configuration at output time is too permissive, allowing event handler attributes like onclick that can trigger JavaScript execution. This violates the principle of defense in depth, where both input and output handling should independently prevent XSS attacks.

Attack Vector

An unauthenticated attacker can exploit this vulnerability by submitting a form through the Responsive Contact Form Builder with specially crafted malicious payloads in field types that are excluded from the lfb_lead_sanitize() whitelist. The payload persists in the WordPress database as a lead entry. When a site administrator navigates to view lead submissions in the WordPress dashboard, the unsanitized content is rendered with the permissive wp_kses() filter, allowing the injected script to execute in the administrator's browser session.

The attack could include anchor tags with onclick event handlers containing malicious JavaScript. Since the scripts run in the context of an authenticated administrator session, attackers could steal session cookies, create rogue admin accounts, modify site content, inject backdoors, or perform any action available to the administrator.

For technical implementation details, refer to the WordPress Plugin Code Reference for ajax-functions.php and the show-lead.php output handling.

Detection Methods for CVE-2026-1454

Indicators of Compromise

• Unexpected anchor tags with onclick attributes in stored lead form entries
• JavaScript code or encoded script payloads within form submission data in the wp_posts or custom lead tables
• Anomalous administrator session activity following lead entry viewing
• Unauthorized admin account creation or privilege modifications coinciding with admin dashboard access

Detection Strategies

• Implement web application firewall (WAF) rules to detect and block XSS payloads in form submissions
• Deploy Content Security Policy (CSP) headers to restrict inline script execution in the WordPress admin area
• Enable database monitoring to alert on suspicious patterns in lead form data, particularly HTML tags with event handlers
• Configure endpoint detection and response (EDR) solutions to monitor for anomalous browser behavior on administrator workstations

Monitoring Recommendations

• Audit WordPress activity logs for unauthorized administrative actions that occur after lead entry review sessions
• Monitor network traffic for suspicious outbound connections from administrator browsers during dashboard usage
• Review form submission logs for patterns indicating automated XSS injection attempts
• Track changes to administrator accounts and permissions for signs of compromise

How to Mitigate CVE-2026-1454

Immediate Actions Required

• Update the Responsive Contact Form Builder & Lead Generation Plugin to the patched version immediately
• Review existing lead form entries in the database for any suspicious content containing script tags or event handlers
• Temporarily disable the plugin if an update is not immediately available
• Regenerate administrator session tokens and verify no unauthorized accounts were created
• Implement Content Security Policy headers to restrict script execution as an additional defense layer

Patch Information

A security patch addressing this vulnerability is available in WordPress Changeset #3462549. Users should update the Responsive Contact Form Builder & Lead Generation Plugin to the latest version via the WordPress admin dashboard or by downloading directly from the WordPress plugin repository.

For comprehensive vulnerability details and remediation guidance, refer to the Wordfence Vulnerability Advisory.

Workarounds

• Temporarily disable the Responsive Contact Form Builder & Lead Generation Plugin until a patch can be applied
• Implement strict WAF rules to filter XSS payloads in all form submission fields
• Add manual Content Security Policy headers to the WordPress admin area to prevent execution of inline scripts
• Limit administrator access to lead form entries and have non-privileged users review submissions where possible
• Consider using an alternative contact form plugin until the vulnerability is remediated

# Add CSP header as temporary mitigation in .htaccess or server configuration
# This restricts inline script execution in the WordPress admin area
Header set Content-Security-Policy "script-src 'self' 'unsafe-eval'; object-src 'none';"