CVE-2026-24836 is a cross-site scripting (XSS) vulnerability classified under CWE-79 that affects the Dnn.Platform, an open-source web content management system within the Microsoft ecosystem. 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 root cause is improper neutralization of input during web page generation, specifically in the handling of richtext content within log notes created by extensions. These log notes can include embedded scripts that execute in the PersonaBar, the administrative interface of Dnn.Platform, when the logs are viewed. Exploitation requires an attacker to have high-level privileges to write such log notes and requires user interaction to trigger script execution by viewing the logs. The vulnerability impacts confidentiality, integrity, and availability by enabling script execution that could lead to session hijacking, privilege escalation, or administrative control takeover. The CVSS v3.1 score is 7.7, reflecting network attack vector, high complexity, required privileges, user interaction, and a scope change. Although no known exploits are currently reported in the wild, the vulnerability poses a significant risk to organizations using affected versions. The issue is resolved in versions 9.13.10 and 10.2.0, which sanitize input properly to prevent script injection in log notes. Due to the administrative nature of the PersonaBar, exploitation could severely compromise the entire CMS environment.

For European organizations, the impact of CVE-2026-24836 can be substantial, especially for those relying on Dnn.Platform for critical web content management. Successful exploitation could allow attackers to execute arbitrary scripts within the administrative interface, potentially leading to full system compromise, data theft, defacement, or disruption of services. This risk is heightened in sectors such as government, healthcare, finance, and large enterprises that use Dnn.Platform for managing sensitive or public-facing content. The vulnerability could also facilitate lateral movement within networks if attackers gain administrative control. Given the high privileges required for exploitation, insider threats or compromised administrator accounts pose a significant risk vector. The availability of a fix means organizations delaying patching remain exposed to potential future attacks once exploit code becomes public. Additionally, the vulnerability could undermine trust in digital services and lead to regulatory compliance issues under GDPR if personal data is compromised.

European organizations should immediately upgrade affected Dnn.Platform instances to version 9.13.10 or 10.2.0 or later, where the vulnerability is fixed. Until patching is complete, restrict extension installation and log note creation privileges to trusted administrators only, minimizing the risk of malicious script injection. Implement strict input validation and sanitization controls on any custom extensions or modules that interact with log notes. Monitor PersonaBar access logs and audit logs for unusual activity or unauthorized access attempts. Employ web application firewalls (WAFs) with rules designed to detect and block XSS payloads targeting the PersonaBar interface. Conduct regular security awareness training for administrators to recognize suspicious behavior and phishing attempts that could lead to credential compromise. Finally, maintain a robust incident response plan to quickly contain and remediate any exploitation attempts.