CVE-2025-65676 is a stored cross-site scripting (XSS) vulnerability identified in Classroomio LMS version 0.1.13. The vulnerability arises from insufficient sanitization of SVG cover images uploaded by authenticated users. Attackers with legitimate access can craft malicious SVG files containing embedded scripts that, when rendered by other users' browsers, execute arbitrary JavaScript code. This stored XSS can lead to session hijacking, credential theft, or unauthorized actions performed on behalf of victims. The vulnerability requires the attacker to have authenticated access to upload content and necessitates victim interaction to trigger the payload. The CVSS 3.1 base score of 5.4 reflects a network attack vector with low attack complexity, requiring privileges and user interaction, and impacting confidentiality and integrity but not availability. No patches or known exploits are currently available, increasing the urgency for organizations to implement interim mitigations. The flaw is categorized under CWE-79, a common and well-understood vulnerability class. Since Classroomio LMS is used primarily in educational environments, the risk extends to students, educators, and administrative staff who may be exposed to malicious content embedded in course materials or user profiles. The stored nature of the XSS means that once the malicious SVG is uploaded, it can affect multiple users over time, increasing the attack surface and potential damage.

For European organizations, especially educational institutions using Classroomio LMS, this vulnerability poses a significant risk to user data confidentiality and integrity. Exploitation could allow attackers to steal session cookies, impersonate users, or perform unauthorized actions within the LMS environment. This could lead to unauthorized access to sensitive educational records, manipulation of course content, or disruption of learning activities. The stored XSS nature means multiple users can be affected once the malicious SVG is uploaded, amplifying the impact. Given the reliance on e-learning platforms across Europe, a successful attack could undermine trust in digital education tools and cause operational disruptions. Although availability is not directly impacted, the potential for data leakage and account compromise is a serious concern. The requirement for authentication and user interaction limits the attack scope but does not eliminate risk, especially in environments with large user bases and frequent content uploads.

European organizations should implement strict input validation and sanitization for all uploaded SVG files, ideally disallowing SVG uploads unless absolutely necessary. Employ server-side sanitization libraries that remove or neutralize embedded scripts within SVGs. Enforce least privilege principles to restrict upload capabilities to trusted users only. Implement Content Security Policy (CSP) headers to limit the execution of inline scripts and reduce the impact of XSS attacks. Conduct regular security audits and monitoring for unusual upload patterns or user behavior indicative of exploitation attempts. Educate users about the risks of uploading untrusted content and encourage reporting of suspicious activities. Until an official patch is released, consider disabling the cover image upload feature or replacing SVG support with safer image formats like PNG or JPEG. Maintain up-to-date backups and incident response plans to quickly address any compromise resulting from exploitation.