CVE-2025-53350 identifies a reflected Cross-site Scripting (XSS) vulnerability in the webjunk Calendar Plus plugin, affecting versions up to and including 1.2.4. The vulnerability stems from improper neutralization of user-supplied input during web page generation, allowing malicious scripts to be injected and executed in the context of a victim's browser session. Reflected XSS typically occurs when input from HTTP requests is immediately included in the response without proper sanitization or encoding. This can enable attackers to craft malicious URLs that, when visited by users, execute arbitrary JavaScript code. Potential consequences include theft of session cookies, redirection to malicious sites, or execution of unauthorized actions within the victim's privileges. Although no public exploits have been reported yet, the vulnerability is publicly disclosed and thus may attract attackers. The affected product, Calendar Plus by webjunk, is a calendar management tool commonly used in web environments for scheduling and event management. The lack of a CVSS score indicates that the vulnerability is newly published and not yet fully assessed. However, the nature of reflected XSS vulnerabilities and their typical impact allows for a severity estimation. The vulnerability does not require authentication or user interaction beyond clicking a crafted link, increasing its risk profile. The absence of patches at the time of disclosure necessitates immediate attention to mitigation strategies to reduce exposure.

For European organizations, exploitation of this reflected XSS vulnerability could lead to significant confidentiality and integrity breaches. Attackers could hijack user sessions, steal sensitive information such as credentials or personal data, and perform unauthorized actions within affected web applications. This is particularly concerning for organizations using Calendar Plus in environments with sensitive scheduling data or integrated with other internal systems. The vulnerability could also facilitate phishing campaigns by injecting deceptive content into legitimate pages, increasing the risk of social engineering attacks. The availability impact is generally low for reflected XSS; however, the reputational damage and potential regulatory consequences under GDPR for data breaches could be substantial. Organizations in sectors such as finance, healthcare, government, and critical infrastructure, which often rely on calendar and scheduling tools, may face elevated risks. The lack of known exploits currently provides a window for proactive mitigation before widespread attacks occur.

1. Monitor webjunk and Calendar Plus vendor channels for official patches and apply them immediately upon release. 2. Implement strict input validation and output encoding on all user-supplied data within the Calendar Plus application to neutralize malicious scripts. 3. Deploy Content Security Policy (CSP) headers to restrict the execution of unauthorized scripts and reduce the impact of potential XSS attacks. 4. Use web application firewalls (WAFs) with updated signatures to detect and block malicious payloads targeting this vulnerability. 5. Educate users about the risks of clicking on suspicious links, especially those related to calendar invitations or scheduling URLs. 6. Conduct security assessments and penetration testing focusing on input handling in Calendar Plus integrations. 7. Consider isolating or restricting access to Calendar Plus interfaces to trusted networks or authenticated users where feasible. 8. Review and enhance logging and monitoring to detect anomalous activities indicative of exploitation attempts.