CVE-2026-24836 is a cross-site scripting (XSS) vulnerability classified under CWE-79, found in the Dnn.Platform content management system (CMS), a Microsoft ecosystem open-source product. The vulnerability exists in versions starting from 9.0.0 up to but not including 9.13.10, and from 10.0.0 up to but not including 10.2.0. The issue arises because extensions can write rich text, including embedded scripts, into log notes without proper input neutralization or sanitization. When these log notes are displayed in the PersonaBar administrative interface, the embedded scripts execute in the context of the logged-in administrator’s browser session. This improper neutralization of input during web page generation allows an attacker with high-level privileges to inject malicious JavaScript code, potentially leading to session hijacking, privilege escalation, or further compromise of the CMS and underlying infrastructure. The vulnerability requires an attacker to have authenticated access with high privileges and to trick a user into interacting with the malicious content, as indicated by the CVSS vector (AV:N/AC:H/PR:H/UI:R/S:C/C:H/I:H/A:H). The vulnerability affects confidentiality, integrity, and availability severely, as malicious scripts can manipulate administrative functions or exfiltrate sensitive data. Versions 9.13.10 and 10.2.0 include fixes that properly sanitize or neutralize the input to prevent script execution. No public exploits have been reported yet, but the high impact and the nature of the vulnerability make it a critical concern for organizations using affected versions.

For European organizations, this vulnerability poses a significant risk, especially for those relying on Dnn.Platform for web content management within their Microsoft-based infrastructure. Successful exploitation could lead to unauthorized access to administrative functions, data leakage, and potential full compromise of the CMS environment. This can disrupt business operations, damage reputation, and lead to regulatory non-compliance, particularly under GDPR due to potential exposure of personal data. The requirement for high privileges and user interaction somewhat limits the attack surface but does not eliminate the risk, as insider threats or compromised credentials could be leveraged. Organizations with public-facing Dnn.Platform instances or those integrated with critical business processes are particularly vulnerable. The absence of known exploits in the wild provides a window for proactive patching and mitigation before widespread attacks occur.

European organizations should immediately identify and inventory all Dnn.Platform instances to determine if they run affected versions (>=9.0.0 and <9.13.10, or >=10.0.0 and <10.2.0). They must prioritize upgrading to versions 9.13.10 or 10.2.0 or later, which contain the necessary fixes. Until patching is complete, restrict access to the PersonaBar interface to trusted administrators only, ideally through network segmentation or VPNs. Implement strict role-based access controls to minimize the number of users with high privileges capable of injecting rich text into log notes. Conduct thorough input validation and sanitization on any custom extensions or modules that write to log notes. Monitor logs for unusual activity or attempts to inject scripts. Educate administrators about phishing and social engineering risks to reduce the likelihood of user interaction with malicious content. Employ Content Security Policy (CSP) headers to limit script execution contexts where feasible. Finally, maintain up-to-date backups and incident response plans to quickly recover from any compromise.