CVE-2025-52485 is a cross-site scripting (XSS) vulnerability identified in the Dnn.Platform, an open-source web content management system widely used within the Microsoft ecosystem. The vulnerability affects versions from 6.0.0 up to, but not including, 10.0.1. The issue arises from improper neutralization of input during web page generation, specifically in the Activity Feed Attachments endpoint. An attacker can craft a malicious request that injects executable scripts into the activity feed, which are then rendered in the feed viewed by users. This type of vulnerability falls under CWE-79, which involves the failure to sanitize or encode user-supplied input, allowing malicious scripts to execute in the context of the victim's browser. The CVSS v4.0 base score is 5.1, indicating a medium severity level. The vector string (AV:N/AC:L/AT:N/PR:L/UI:P/VC:N/VI:N/VA:N/SC:L/SI:L/SA:N) shows that the attack can be performed remotely over the network with low attack complexity, requires low privileges but does require user interaction (UI:P), and impacts system confidentiality, integrity, and availability to a limited extent. There are no known exploits in the wild at the time of publication, and the vulnerability has been patched in version 10.0.1 of Dnn.Platform. The vulnerability does not require authentication but does require that a user views the maliciously crafted activity feed to trigger script execution. This can lead to session hijacking, defacement, or redirection to malicious sites, depending on the payload. The scope is limited to the affected versions and the specific endpoint, but given the popularity of Dnn.Platform in certain sectors, the risk is non-negligible.

For European organizations using Dnn.Platform versions prior to 10.0.1, this vulnerability poses a risk of client-side script execution that can compromise user sessions, steal sensitive information, or perform unauthorized actions on behalf of users. This is particularly impactful for organizations relying on Dnn for internal portals, intranets, or public-facing websites where user trust and data confidentiality are critical. The vulnerability could facilitate phishing campaigns, credential theft, or unauthorized access to internal resources. While the vulnerability does not directly compromise server integrity or availability, the indirect effects of successful exploitation—such as reputational damage, regulatory non-compliance (e.g., GDPR breaches due to data leakage), and operational disruption—can be significant. The requirement for user interaction means that social engineering or targeted attacks may increase the likelihood of exploitation. European organizations in sectors such as government, finance, healthcare, and education, which often use CMS platforms like Dnn for communication and content management, may face elevated risks. Additionally, the medium CVSS score suggests that while the vulnerability is not critical, it should be addressed promptly to prevent exploitation.

1. Immediate upgrade: Organizations should upgrade all instances of Dnn.Platform to version 10.0.1 or later, where the vulnerability is patched. 2. Input validation and output encoding: Review and enhance server-side input validation and output encoding mechanisms, especially for the Activity Feed Attachments endpoint, to prevent injection of malicious scripts. 3. Content Security Policy (CSP): Implement a strict CSP header to restrict the execution of unauthorized scripts and reduce the impact of potential XSS attacks. 4. User awareness training: Educate users about the risks of interacting with suspicious activity feeds or links, emphasizing caution with unexpected or unusual content. 5. Web Application Firewall (WAF): Deploy or update WAF rules to detect and block malicious payloads targeting the vulnerable endpoint. 6. Monitoring and logging: Enable detailed logging of activity feed interactions and monitor for anomalous requests or patterns indicative of exploitation attempts. 7. Segmentation and least privilege: Limit the exposure of the Dnn platform to only necessary users and networks, reducing the attack surface. 8. Incident response readiness: Prepare incident response plans to quickly address any detected exploitation, including session invalidation and forensic analysis.