CVE-2025-2748: Kentico Xperience XSS Vulnerability

CVE-2025-2748 Overview

CVE-2025-2748 is a stored Cross-Site Scripting (XSS) vulnerability in Kentico Xperience, a digital experience platform widely used for enterprise content management and digital marketing. The vulnerability exists in the multiple-file upload functionality, where the application fails to fully validate or filter uploaded files. This allows attackers to upload malicious files containing JavaScript code that will be executed in the context of other users' browsers when they access the uploaded content.

Critical Impact

Attackers can inject persistent malicious scripts through file uploads, potentially compromising administrator sessions, stealing credentials, or performing unauthorized actions on behalf of authenticated users.

Affected Products

• Kentico Xperience through version 13.0.178

Discovery Timeline

• 2025-03-24 - CVE CVE-2025-2748 published to NVD
• 2025-12-27 - Last updated in NVD database

Technical Details for CVE-2025-2748

Vulnerability Analysis

This stored XSS vulnerability (CWE-79) stems from insufficient input validation in the multiple-file upload feature of Kentico Xperience. When users upload files through this functionality, the application does not adequately sanitize or validate the file contents, allowing malicious scripts to be stored on the server. These scripts are then executed when other users view or interact with the uploaded files, making this a persistent attack vector.

The vulnerability requires user interaction for exploitation—a victim must access the page or resource containing the malicious uploaded content. Due to the scope change in the attack, the malicious script can affect resources beyond the vulnerable component, potentially impacting the confidentiality and integrity of data in the victim's browser session.

Root Cause

The root cause of CVE-2025-2748 is improper input validation in the file upload processing pipeline. The application fails to:

1. Properly validate file content types against their actual contents
2. Sanitize or encode potentially dangerous content within uploaded files
3. Implement Content Security Policy headers that would mitigate script execution
4. Restrict the types of files that can be uploaded to safe formats only

This allows attackers to bypass file type restrictions and inject executable JavaScript code that persists in the application's storage.

Attack Vector

The attack is conducted over the network without requiring authentication privileges. An attacker can exploit this vulnerability by:

1. Identifying the multiple-file upload functionality in a Kentico Xperience installation
2. Crafting a malicious file containing JavaScript payloads (such as an SVG with embedded script tags or an HTML file with malicious code)
3. Uploading the malicious file through the vulnerable upload mechanism
4. Waiting for or socially engineering a victim to access the uploaded content
5. The malicious script executes in the victim's browser context, potentially stealing session tokens, performing actions as the victim, or redirecting to phishing pages

The attack typically involves uploading files with embedded <script> tags or event handlers that execute when the file content is rendered by the browser.

Detection Methods for CVE-2025-2748

Indicators of Compromise

• Unusual file uploads containing HTML, SVG, or other files with embedded JavaScript code
• Web server logs showing access to suspicious uploaded files from multiple IP addresses
• User reports of unexpected behavior, pop-ups, or redirects when viewing uploaded content
• Audit logs indicating file uploads with potentially malicious content types

Detection Strategies

• Implement file content inspection on uploads to detect embedded scripts or suspicious patterns
• Monitor for file uploads with mismatched MIME types (e.g., image extension with HTML content)
• Deploy Web Application Firewall (WAF) rules to detect XSS patterns in file upload requests
• Enable detailed logging of all file upload activities including user, timestamp, and file metadata

Monitoring Recommendations

• Configure alerts for uploads of file types commonly used in XSS attacks (SVG, HTML, XML)
• Monitor for unusual patterns in the CMSAttachment or media library tables
• Review access logs for suspicious activity around uploaded file endpoints
• Implement real-time scanning of uploaded content for malicious payloads

How to Mitigate CVE-2025-2748

Immediate Actions Required

• Upgrade Kentico Xperience to a patched version beyond 13.0.178
• Review and audit all existing uploaded files for potentially malicious content
• Implement strict Content Security Policy headers to mitigate script execution
• Restrict file upload functionality to authenticated and authorized users only
• Consider temporarily disabling the multiple-file upload feature until patched

Patch Information

Kentico has released hotfixes to address this vulnerability. Administrators should apply the latest security updates available through the Kentico Hotfixes Download page. It is strongly recommended to upgrade to a version newer than 13.0.178 to ensure protection against this stored XSS vulnerability.

Workarounds

• Implement server-side file content validation to strip or reject files containing script content
• Configure the web server to serve uploaded files with Content-Disposition: attachment headers to prevent inline rendering
• Deploy a Web Application Firewall (WAF) with XSS detection rules for file upload endpoints
• Restrict allowed file types to a whitelist of safe formats (e.g., JPEG, PNG, PDF) and validate content matches the extension
• Enable Content Security Policy headers with strict script-src directives to prevent inline script execution

# Example IIS web.config configuration to add security headers
# Add to the system.webServer section
<httpProtocol>
  <customHeaders>
    <add name="Content-Security-Policy" value="default-src 'self'; script-src 'self'; object-src 'none'" />
    <add name="X-Content-Type-Options" value="nosniff" />
  </customHeaders>
</httpProtocol>