CVE-2025-54676 is a stored Cross-site Scripting (XSS) vulnerability classified under CWE-79, affecting the vcita Online Booking & Scheduling Calendar plugin for WordPress. This vulnerability arises from improper neutralization of user-supplied input during web page generation, allowing malicious scripts to be stored and later executed in the context of users visiting affected pages. The affected versions include all versions up to 4.5.3. The vulnerability requires low privileges (PR:L) and user interaction (UI:R) to exploit, but it can lead to a complete compromise of confidentiality, integrity, and availability within the scope of the affected web application. The CVSS v3.1 base score is 6.5 (medium severity), with attack vector network (AV:N), low attack complexity (AC:L), and scope changed (S:C), indicating that exploitation can affect resources beyond the initially vulnerable component. Stored XSS vulnerabilities are particularly dangerous because malicious payloads persist on the server and can affect multiple users, including administrators, potentially leading to session hijacking, credential theft, defacement, or further exploitation of the underlying system. The vulnerability does not currently have known exploits in the wild, and no patches have been linked yet, suggesting that mitigation and patching efforts should be prioritized to prevent exploitation.

For European organizations, especially those using WordPress with the vcita Online Booking & Scheduling Calendar plugin, this vulnerability poses a significant risk. Many European businesses in sectors such as healthcare, education, professional services, and retail rely on online booking systems to manage appointments and customer interactions. Exploitation could lead to unauthorized access to sensitive customer data, session hijacking of administrative accounts, and defacement or disruption of online services, damaging reputation and customer trust. Given the GDPR regulatory environment, any data breach resulting from this vulnerability could lead to substantial fines and legal consequences. The medium severity rating indicates that while the vulnerability is not trivial, it requires some user interaction and privileges, which somewhat limits the attack surface but does not eliminate the risk. The potential for scope change means that attackers could leverage this vulnerability to impact other components or data beyond the plugin itself, increasing the overall threat to organizational IT infrastructure.

European organizations should take immediate steps to mitigate this vulnerability. First, monitor vcita and WordPress security advisories for official patches and apply them promptly once available. Until patches are released, implement strict input validation and output encoding on all user-supplied data related to the booking calendar, especially in custom integrations or themes. Employ Web Application Firewalls (WAFs) with rules targeting common XSS payloads to provide a temporary protective barrier. Limit user privileges to the minimum necessary to reduce the risk of exploitation by low-privilege users. Conduct thorough security audits and penetration testing focusing on the booking system to identify and remediate any additional injection points. Educate staff and users about the risks of clicking suspicious links or submitting unexpected inputs. Finally, maintain regular backups and incident response plans to quickly recover in case of exploitation.