CVE-2026-24836: DNN (DotNetNuke) XSS Vulnerability

CVE-2026-24836 Overview

DNN (formerly DotNetNuke) is an open-source web content management platform (CMS) in the Microsoft ecosystem. A stored Cross-Site Scripting (XSS) vulnerability has been identified in versions starting from 9.0.0 through versions prior to 9.13.10 and 10.2.0. The vulnerability allows extensions to write richtext content in log notes, which can include malicious scripts that execute in the PersonaBar administrative interface when displayed.

Critical Impact

Attackers with extension privileges can inject malicious scripts into log notes that execute in the context of administrative users accessing the PersonaBar, potentially leading to session hijacking, privilege escalation, and administrative account compromise.

Affected Products

• DNN Platform versions 9.0.0 to 9.13.9
• DNN Platform versions 10.0.0 to 10.1.x

Discovery Timeline

• 2026-01-28 - CVE CVE-2026-24836 published to NVD
• 2026-01-29 - Last updated in NVD database

Technical Details for CVE-2026-24836

Vulnerability Analysis

This vulnerability is classified as CWE-79 (Improper Neutralization of Input During Web Page Generation), commonly known as Cross-Site Scripting (XSS). The flaw exists in how DNN handles richtext content within log notes functionality. Extensions are permitted to write richtext data to log entries, but the content is not properly sanitized before being rendered in the PersonaBar administrative interface.

The stored nature of this XSS vulnerability makes it particularly dangerous in administrative contexts. When an administrator views the log entries through the PersonaBar, any embedded script code executes with the privileges of that administrator's session. This attack requires network access and some level of privileged access to write to log notes, combined with user interaction from an administrator viewing the logs.

Root Cause

The root cause lies in insufficient output encoding and input sanitization when processing richtext content in log notes. The DNN platform fails to properly escape or sanitize HTML and JavaScript content before storing it in log entries and subsequently rendering it in the PersonaBar interface. This allows attackers to embed arbitrary script content that persists in the system and executes when viewed.

Attack Vector

The attack vector is network-based and requires an authenticated attacker with privileges to write extension log notes. The attacker crafts malicious richtext content containing JavaScript payloads and submits it through the extension logging mechanism. When an administrator navigates to view log entries in the PersonaBar, the stored script executes in their browser context.

The vulnerability mechanism involves injecting script tags or JavaScript event handlers within richtext log note content. When the PersonaBar renders these log entries without proper sanitization, the browser interprets and executes the malicious code. For detailed technical information, see the GitHub Security Advisory.

Detection Methods for CVE-2026-24836

Indicators of Compromise

• Unusual JavaScript or HTML tags present in DNN log note entries
• Unexpected outbound network connections originating from administrator browser sessions when viewing logs
• Log entries containing encoded script content (e.g., base64-encoded payloads, HTML entity encoded scripts)
• Evidence of session token exfiltration or unauthorized administrative actions following log review

Detection Strategies

• Implement web application firewalls (WAF) with rules to detect XSS payloads in log-related endpoints
• Enable Content Security Policy (CSP) headers to restrict script execution sources in administrative interfaces
• Monitor for anomalous log entry content containing script tags, event handlers, or encoded payloads
• Deploy endpoint detection to identify browser-based script execution anomalies in administrative sessions

Monitoring Recommendations

• Review DNN log entries for suspicious richtext content containing <script>, onclick, onerror, or similar patterns
• Monitor network traffic from administrator workstations for unexpected external connections during PersonaBar usage
• Implement logging and alerting for any modifications to extension log entries
• Regularly audit user accounts with extension management privileges

How to Mitigate CVE-2026-24836

Immediate Actions Required

• Upgrade DNN Platform to version 9.13.10 or 10.2.0 or later immediately
• Review existing log entries for any suspicious or malicious content before upgrading
• Audit accounts with extension privileges and verify their legitimacy
• Consider restricting access to the PersonaBar until patching is complete

Patch Information

DNN Software has released patched versions that address this stored XSS vulnerability. Versions 9.13.10 and 10.2.0 contain the fix that properly sanitizes richtext content in log notes before rendering in the PersonaBar. Organizations should upgrade to these versions or later to remediate the vulnerability. For complete patch details and upgrade instructions, refer to the GitHub Security Advisory.

Workarounds

• Restrict extension installation and management privileges to only essential trusted personnel
• Implement Content Security Policy (CSP) headers at the web server level to mitigate script execution
• Deploy a web application firewall with XSS detection rules in front of the DNN installation
• Consider temporarily disabling or limiting access to the PersonaBar log viewing functionality until patching is possible

# Example: Configure IIS to add Content-Security-Policy header
# Add to web.config in the DNN installation root
# <system.webServer>
#   <httpProtocol>
#     <customHeaders>
#       <add name="Content-Security-Policy" value="script-src 'self'; object-src 'none';" />
#     </customHeaders>
#   </httpProtocol>
# </system.webServer>