CVE-2025-6251

Executive Summary

CVE-2025-6251 is a Stored Cross-Site Scripting (XSS) vulnerability in the Royal Elementor Addons and Templates plugin for WordPress. The flaw resides in the insufficient sanitization of the $item['field_id'] parameter, allowing authenticated attackers with Contributor-level access or higher to inject arbitrary web scripts. These scripts execute when any user accesses the compromised page. The vulnerability affects all versions up to and including 1.7.1036. As of this report, no official patch has been released, and no public exploit code is available. The CVSS score is 6.4 (Medium), with a low EPSS probability of 0.0%.

Supply Chain & Package Security

This vulnerability is specific to the WordPress ecosystem and the Royal Elementor Addons plugin. It is not related to Apache or Nginx. The plugin is distributed via the WordPress plugin repository and third-party marketplaces. Users should verify the integrity of their plugin files and monitor for updates from the vendor.

CVSS Breakdown & Threat Level

• Attack Vector (AV): Network (N) – The attack is carried out over the network.
• Attack Complexity (AC): Low (L) – No special conditions are required.
• Privileges Required (PR): Low (L) – The attacker needs Contributor-level access.
• User Interaction (UI): None (N) – No user action is needed for the script to execute.
• Scope (S): Changed (C) – The vulnerability impacts resources beyond the original scope.
• Confidentiality (C): Low (L) – Limited data exposure.
• Integrity (I): Low (L) – Limited ability to modify data.
• Availability (A): None (N) – No impact on availability.

Threat Level: Medium. The requirement for authenticated access reduces the attack surface, but the stored nature of the XSS can lead to widespread impact if exploited on a high-traffic page.

Deep Dive & Mechanics

The vulnerability exists in the form builder or similar component of the Royal Elementor Addons plugin. When processing form submissions or widget settings, the plugin uses the $item['field_id'] parameter to generate HTML attributes. Due to insufficient input sanitization and output escaping, an attacker can inject malicious JavaScript code into this field.

Attack Flow:

1. An authenticated user with Contributor-level access creates or edits a page using the Royal Elementor Addons form widget.
2. The attacker crafts a payload in the field_id parameter, such as "><script>alert('XSS')</script>.
3. The plugin stores this payload in the database without proper sanitization.
4. When any user (including administrators) visits the page, the injected script executes in their browser.

Root Cause: The plugin fails to use WordPress's built-in escaping functions (e.g., esc_attr(), esc_html()) on the $item['field_id'] value before outputting it in the HTML.

Vulnerable vs. Patched Code

Vulnerable Code (Example):

// In a form rendering function
echo '<input type="text" name="' . $item['field_id'] . '" />';

Patched Code (Expected):

// Properly escaped
echo '<input type="text" name="' . esc_attr( $item['field_id'] ) . '" />';

The patched version would use esc_attr() to neutralize any HTML or JavaScript characters.

Exploitation & Lab Setup

Red Team (Exploitation)

Prerequisites:

• WordPress instance with Royal Elementor Addons <= 1.7.1036.
• An account with Contributor-level access or higher.

Steps:

1. Log in to WordPress as a Contributor.
2. Create a new page or edit an existing one.
3. Add the Royal Elementor Addons form widget.
4. In the form field settings, set the Field ID to a malicious payload:

   "><script>alert(document.cookie)</script>
   

5. Save and publish the page.
6. When any user visits the page, the script executes.

Proof of Concept (No public exploit available):

<!-- Payload for field_id -->
"><img src=x onerror=alert('XSS')>

Blue Team (Detection & Prevention)

Detection:

• Monitor for unusual field_id values in form submissions.
• Look for pages containing script tags or event handlers in form field attributes.
• Use Web Application Firewall (WAF) rules to block common XSS patterns.

Prevention:

• Apply input validation and output escaping on all user-supplied data.
• Restrict Contributor-level access to trusted users only.
• Use Content Security Policy (CSP) headers to mitigate script execution.

Indicators of Compromise (IOCs)

• File Indicators:

  • Modified plugin files in /wp-content/plugins/royal-elementor-addons/
  • Suspicious entries in the wp_posts or wp_postmeta tables containing script tags.

• Network Indicators:

  • HTTP requests to the WordPress site with field_id parameters containing <script> or onerror= patterns.

• Behavioral Indicators:

  • Unexpected JavaScript execution on pages using the Royal Elementor Addons form widget.
  • Alerts from security plugins (e.g., Wordfence) flagging XSS attempts.

Detection Engineering

YARA Rule

rule CVE_2025_6251_Stored_XSS {
    meta:
        description = "Detects stored XSS payloads in Royal Elementor Addons field_id"
        author = "Valters IT"
        date = "2025-01-01"
        reference = "CVE-2025-6251"
    strings:
        $payload1 = /<script[^>]*>.*?<\/script>/is
        $payload2 = /onerror\s*=\s*["']?[^"'\s>]+/is
        $payload3 = /onload\s*=\s*["']?[^"'\s>]+/is
    condition:
        any of them
}

Sigma Rule

title: CVE-2025-6251 Stored XSS in Royal Elementor Addons
id: 8a4b3c2d-1e5f-6a7b-8c9d-0e1f2a3b4c5d
status: experimental
description: Detects stored XSS attempts via field_id parameter in Royal Elementor Addons
author: Valters IT
date: 2025-01-01
logsource:
    category: webserver
    product: apache
detection:
    selection:
        cs-method: 'POST'
        cs-uri-query|contains: 'field_id'
        cs-uri-query|re: '(<script|onerror|onload)'
    condition: selection
falsepositives:
    - Legitimate use of JavaScript in form fields (rare)
level: high

Suricata Rule

alert http any any -> any any (msg:"CVE-2025-6251 Stored XSS in Royal Elementor Addons"; flow:to_server,established; content:"field_id"; http_client_body; pcre:"/(<script|onerror|onload)/i"; sid:1000001; rev:1;)

Remediation & Mitigation

Immediate Actions:

1. Disable the plugin if it is not critical to operations.
2. Restrict Contributor-level access to only trusted users.
3. Apply a virtual patch using a WAF to block XSS payloads in field_id parameters.

Long-term Fix:

• Monitor the vendor's website for a patched version (expected to be > 1.7.1036).
• Once available, update the plugin immediately.
• Conduct a security audit of all custom fields and form inputs.

Workaround:

• Use a security plugin like Wordfence to add an additional layer of XSS protection.
• Implement a Content Security Policy (CSP) that blocks inline scripts.

Valters IT