CVE-2026-23840 identifies a critical security flaw in the leepeuker movary web application, a platform designed for tracking, rating, and exploring movie watch histories. The vulnerability stems from improper input validation (CWE-20) of the `?categoryDeleted=` URL parameter, which allows attackers to inject arbitrary JavaScript code, resulting in a cross-site scripting (XSS) attack (CWE-79). This flaw affects all versions prior to 0.70.0, where the issue has been resolved. The vulnerability can be exploited remotely without requiring authentication, though it requires user interaction such as clicking a crafted link. The CVSS v3.1 base score of 9.3 reflects the high impact on confidentiality and integrity, with no impact on availability. Successful exploitation could allow attackers to steal session cookies, perform actions on behalf of users, or deliver malicious payloads, potentially compromising user accounts and data. While no public exploits have been reported yet, the vulnerability’s nature and severity make it a high-risk target for attackers. The vulnerability is classified under CWE-20 (Improper Input Validation) and CWE-79 (Cross-Site Scripting), emphasizing the failure to properly sanitize user-supplied input before rendering it in the web interface. The patch for this vulnerability is included in movary version 0.70.0, which should be applied promptly to mitigate risk.

For European organizations, the impact of CVE-2026-23840 can be significant, especially for those using movary to manage movie watch histories or related media services. Exploitation could lead to unauthorized access to user accounts, theft of sensitive information such as session tokens, and manipulation of user data. This can result in privacy breaches, reputational damage, and potential regulatory non-compliance under GDPR due to exposure of personal data. Media companies, entertainment platforms, and cultural institutions that integrate movary or similar applications could face operational disruptions and loss of user trust. The vulnerability’s ability to compromise confidentiality and integrity without requiring authentication increases the risk profile. Additionally, attackers could leverage this XSS flaw as a pivot point for further attacks within an organization’s network. Although availability is not directly affected, the indirect consequences of data breaches and account compromises can lead to service interruptions and increased incident response costs.

European organizations should immediately upgrade all instances of movary to version 0.70.0 or later to remediate the vulnerability. In addition to patching, implement strict input validation and output encoding on all user-supplied data, especially URL parameters like `categoryDeleted`. Employ Content Security Policy (CSP) headers to restrict the execution of unauthorized scripts and reduce the impact of potential XSS attacks. Conduct regular security audits and penetration testing focused on input validation weaknesses. Educate users about the risks of clicking on suspicious links and monitor web application logs for unusual activity related to the vulnerable parameter. Deploy web application firewalls (WAFs) with rules designed to detect and block XSS payloads targeting movary. Finally, maintain an incident response plan that includes procedures for handling XSS incidents and potential data breaches.