CVE-2023-53876 is a file upload vulnerability affecting Creativeitem's Academy LMS version 6.1. The flaw arises from insufficient validation and sanitization of uploaded files in the profile avatar upload feature, allowing authenticated users to upload SVG files containing embedded JavaScript code. SVG files are XML-based vector images that can include script elements, which, if not properly sanitized, can execute malicious JavaScript when rendered by a victim's browser. Attackers exploit this by modifying file extensions and embedding stored cross-site scripting (XSS) payloads within the SVG, which are then stored on the server and served to other users. When other users view the affected profile or page, the malicious script executes in their browser context, potentially leading to session hijacking, credential theft, or unauthorized actions within the LMS environment. The vulnerability requires the attacker to have valid user credentials (authenticated access) and some user interaction (viewing the malicious avatar). The CVSS 4.0 base score is 5.1, reflecting medium severity, with network attack vector, low attack complexity, no privileges required beyond authentication, and partial impact on confidentiality and integrity. No public exploits or patches are currently available, increasing the urgency for organizations to implement mitigations. The vulnerability's scope is limited to the LMS application but can have significant consequences in environments where sensitive educational data and user credentials are stored.

For European organizations, particularly educational institutions, training providers, and corporate LMS users, this vulnerability poses a risk of unauthorized script execution within the LMS platform. Exploitation could lead to theft of user credentials, session hijacking, and unauthorized access to sensitive educational content or personal data. This can undermine user trust, lead to data breaches, and disrupt learning activities. Given the authenticated nature of the exploit, insider threats or compromised accounts could be leveraged to escalate attacks. The impact on confidentiality and integrity is moderate, while availability impact is minimal. However, the stored XSS could facilitate further attacks such as phishing or lateral movement within the LMS environment. Organizations relying on Academy LMS 6.1 without adequate controls may face reputational damage and regulatory scrutiny under GDPR if personal data is compromised.

1. Immediately restrict the types of files allowed for upload in the profile avatar feature, explicitly blocking SVG files or any files capable of containing executable code. 2. Implement strict server-side validation and sanitization of uploaded files, including content-type verification and scanning for embedded scripts within SVGs. 3. Employ Content Security Policy (CSP) headers to limit the execution of inline scripts and reduce the impact of XSS attacks. 4. Enforce least privilege access controls and monitor user activities to detect anomalous upload behavior. 5. Educate users about the risks of uploading files and encourage reporting of suspicious profiles. 6. If possible, upgrade to a patched version of Academy LMS once available or apply vendor-provided patches promptly. 7. Conduct regular security assessments and penetration testing focused on file upload functionalities. 8. Implement multi-factor authentication to reduce the risk of account compromise that could facilitate exploitation.