CVE-2024-23941 is a cross-site scripting (XSS) vulnerability identified in Intermesh BV's Group Office product, affecting versions prior to v6.6.182, v6.7.64, and v6.8.31. This vulnerability allows a remote authenticated attacker to inject and execute arbitrary scripts in the web browser of a user who logs into the affected Group Office instance. The vulnerability falls under CWE-79, which is a common weakness related to improper neutralization of input leading to XSS attacks. The attack vector is network-based (AV:N), requires low attack complexity (AC:L), and requires the attacker to have some level of privileges (PR:L) and user interaction (UI:R) since the victim must log in for the malicious script to execute. The scope is changed (S:C), meaning the vulnerability affects components beyond the initially vulnerable component. The impact affects confidentiality and integrity (C:L/I:L) but not availability (A:N). The CVSS score is 5.4, indicating a medium severity level. Although no known exploits are currently reported in the wild, the vulnerability could be leveraged to steal session cookies, perform actions on behalf of the victim, or conduct phishing attacks within the context of the Group Office web application. Since Group Office is a web-based collaboration and groupware platform used for email, calendar, file sharing, and project management, exploitation could lead to unauthorized access to sensitive organizational data and user credentials.

For European organizations using Group Office, this vulnerability poses a significant risk to the confidentiality and integrity of internal communications and data. Successful exploitation could allow attackers to hijack user sessions, steal sensitive information, or manipulate data within the platform. Given that Group Office is often used by small to medium enterprises and public sector organizations for collaboration, the impact could extend to disruption of business processes, exposure of personal data protected under GDPR, and potential reputational damage. The requirement for authentication limits the attack surface to legitimate users or compromised accounts, but insider threats or phishing campaigns could facilitate exploitation. The medium severity rating suggests that while the vulnerability is not critical, it should be addressed promptly to prevent escalation or lateral movement within networks. Additionally, the scope change indicates that the vulnerability could affect multiple components or users beyond the initially targeted system, increasing potential impact.

European organizations should immediately upgrade Group Office to versions v6.6.182, v6.7.64, or v6.8.31 or later, where the vulnerability has been fixed. Until patching is possible, organizations should implement strict input validation and output encoding on user-supplied data within the application, if feasible. Employing Content Security Policy (CSP) headers can help mitigate the impact of XSS by restricting the execution of unauthorized scripts. Organizations should also enforce strong authentication mechanisms and monitor user activity for suspicious behavior indicative of session hijacking or unauthorized access. Regular security awareness training should be conducted to reduce the risk of phishing attacks that could facilitate exploitation. Network segmentation and limiting access to the Group Office application to trusted networks or VPN users can reduce exposure. Finally, logging and alerting on anomalous web application behavior can help detect exploitation attempts early.