CVE-2025-52131 is a medium severity vulnerability classified under CWE-79, indicating an improper neutralization of input during web page generation, commonly known as Cross-site Scripting (XSS). This vulnerability affects the Mocca Calendar application, a component of the xwiki-contrib project, specifically versions before 2.15. The flaw arises because the application fails to properly sanitize user-supplied input in the background or text color fields. An attacker can exploit this by injecting malicious scripts into these fields, which are then executed in the context of other users viewing the calendar. The CVSS 3.1 base score is 6.4, reflecting a network attack vector (AV:N), low attack complexity (AC:L), requiring low privileges (PR:L), no user interaction (UI:N), with a scope change (S:C), and limited confidentiality and integrity impact (C:L/I:L) but no availability impact (A:N). The vulnerability allows an attacker with some level of access to the system to execute arbitrary scripts in the victim's browser, potentially leading to session hijacking, data theft, or further exploitation within the affected web application environment. Although no known exploits are currently reported in the wild, the vulnerability's presence in a widely used collaboration tool like XWiki's Mocca Calendar raises concerns about potential targeted attacks, especially in environments where this calendar is used for scheduling and sharing sensitive organizational information.

For European organizations utilizing XWiki with the Mocca Calendar extension, this vulnerability poses a risk to the confidentiality and integrity of internal communications and scheduling data. Exploitation could lead to unauthorized disclosure of sensitive information, session hijacking, or the spread of malicious payloads within corporate networks. Given that many European public sector entities, educational institutions, and enterprises use XWiki for collaboration, the impact could extend to disruption of workflows and potential reputational damage. The scope change in the CVSS vector indicates that exploitation can affect resources beyond the initially compromised component, potentially allowing attackers to escalate privileges or move laterally within the application. While availability is not directly impacted, the indirect consequences of data leakage or trust erosion could be significant. Furthermore, the lack of required user interaction means that attacks could be automated or triggered simply by viewing a compromised calendar entry, increasing the risk of widespread impact within organizations.

Organizations should prioritize upgrading the Mocca Calendar application to version 2.15 or later, where this vulnerability is addressed. In the absence of an immediate patch, administrators should implement strict input validation and sanitization on the background and text color fields at the application or web server level to neutralize potentially malicious scripts. Employing Content Security Policy (CSP) headers can help mitigate the impact of XSS by restricting the execution of unauthorized scripts. Additionally, restricting calendar editing permissions to trusted users and monitoring logs for unusual input patterns can reduce the attack surface. Regular security audits and penetration testing focusing on web application input handling will help identify similar vulnerabilities. User education about the risks of interacting with untrusted content within internal tools can further reduce exploitation likelihood.