CVE-2025-45314 is a cross-site scripting (XSS) vulnerability identified in the /Calendar endpoint of hortusfox-web version 4.4. This vulnerability arises from improper input validation or sanitization in the add function of the Calendar endpoint, allowing an attacker to inject crafted JavaScript payloads. When a victim user accesses the affected endpoint, the malicious script executes within their browser context. This can lead to session hijacking, credential theft, unauthorized actions on behalf of the user, or delivery of further malicious payloads such as malware. The vulnerability is client-side and exploits the trust relationship between the user and the web application. Although no specific affected versions beyond v4.4 are listed, the lack of patch links suggests that a fix may not yet be available. No known exploits are currently reported in the wild, but the nature of XSS vulnerabilities makes them relatively easy to exploit once discovered, especially if user interaction with the vulnerable endpoint is common. The absence of a CVSS score means severity must be assessed based on impact and exploitability factors.

For European organizations using hortusfox-web v4.4, this XSS vulnerability poses a significant risk to confidentiality and integrity of user sessions and data. Attackers could leverage this flaw to steal sensitive information such as authentication tokens, personal data, or perform unauthorized actions within the application context. This could lead to data breaches, loss of user trust, and potential regulatory non-compliance under GDPR if personal data is compromised. Additionally, the vulnerability could be used as a pivot point for further attacks within the organization's network. Since hortusfox-web is a web-based application, any organization relying on it for calendar or scheduling functions may face operational disruptions or reputational damage. The impact is heightened in sectors with strict data protection requirements such as finance, healthcare, and government institutions prevalent in Europe.

Organizations should immediately audit their use of hortusfox-web, specifically version 4.4, and restrict access to the /Calendar endpoint where feasible. Implementing strict input validation and output encoding on the add function is critical to prevent injection of malicious scripts. Web Application Firewalls (WAFs) can be configured to detect and block typical XSS payload patterns targeting this endpoint. User education to recognize suspicious activity and limiting browser privileges (e.g., disabling unnecessary scripting) can reduce risk. Monitoring logs for unusual requests to the /Calendar endpoint may help detect exploitation attempts. Until an official patch is released, consider isolating or disabling the vulnerable functionality or migrating to a more secure version or alternative solution. Regular security assessments and penetration testing focused on client-side vulnerabilities should be conducted to identify similar issues.