CVE-2025-3962 is a cross-site scripting (XSS) vulnerability identified in version 1.0 of the withstars Books-Management-System, specifically within the /api/comment/add endpoint of the Comment Handler component. The vulnerability arises from improper sanitization or validation of the 'content' argument submitted to this API endpoint, allowing an attacker to inject malicious scripts. Since the attack vector is remote and does not require authentication, an attacker can exploit this flaw by sending crafted requests to the vulnerable API to execute arbitrary JavaScript in the context of users who view the affected comments. The vulnerability is classified as 'problematic' with a CVSS 4.0 base score of 5.1 (medium severity), reflecting moderate impact and ease of exploitation. Notably, the product version affected is no longer supported by the vendor, meaning no official patches or updates are available to remediate this issue. Although no known exploits have been reported in the wild, the public disclosure of the vulnerability increases the risk of exploitation. The XSS flaw primarily threatens the integrity and confidentiality of user sessions and data by enabling theft of cookies, session tokens, or performing actions on behalf of authenticated users. The vulnerability does not affect system availability directly but can facilitate further attacks such as phishing or privilege escalation if chained with other vulnerabilities. The lack of vendor support complicates mitigation efforts, requiring organizations to implement compensating controls or consider migration to supported alternatives.

For European organizations using withstars Books-Management-System 1.0, this vulnerability poses a moderate risk primarily to web application security and user data confidentiality. Exploitation could lead to session hijacking, unauthorized actions, or distribution of malicious content to users, undermining trust and potentially causing reputational damage. Educational institutions, libraries, or businesses relying on this system for book management and user interaction are at risk of targeted attacks, especially if sensitive user information is accessible through the platform. The absence of vendor support means that organizations cannot rely on official patches, increasing the likelihood of prolonged exposure. Additionally, regulatory frameworks such as GDPR impose strict requirements on data protection; exploitation of this vulnerability leading to data breaches could result in legal and financial penalties. While the vulnerability does not directly impact system availability, the potential for indirect consequences such as phishing campaigns or malware distribution could have broader operational impacts. Organizations with high user interaction on the platform are particularly vulnerable to exploitation attempts.

Given the lack of official patches, European organizations should implement the following specific mitigations: 1) Deploy Web Application Firewalls (WAFs) with custom rules to detect and block malicious payloads targeting the /api/comment/add endpoint, focusing on script injection patterns in the 'content' parameter. 2) Implement strict Content Security Policy (CSP) headers to restrict the execution of unauthorized scripts in browsers accessing the application, thereby limiting the impact of XSS attacks. 3) Sanitize and validate all user inputs at the application layer, potentially by introducing additional input filtering proxies or middleware if source code modification is not feasible. 4) Monitor application logs and network traffic for unusual activity indicative of exploitation attempts, such as repeated suspicious comment submissions. 5) Educate users about the risks of clicking on unexpected links or executing scripts received via the platform. 6) Consider migrating to a supported and actively maintained book management system to eliminate reliance on vulnerable software. 7) If feasible, isolate the vulnerable system within a segmented network zone to limit exposure and access. 8) Regularly review and update incident response plans to address potential exploitation scenarios involving XSS attacks.