CVE-2025-3999 is a cross-site scripting (XSS) vulnerability identified in the Seeyon Zhiyuan OA Web Application System version 8.1 SP2. The vulnerability arises from improper handling of URL parameters in the file located at seeyon\opt\Seeyon\A8\ApacheJetspeed\webapps\seeyon\common\js\addDate\date.jsp. Specifically, the URL parameter handler does not adequately sanitize user-supplied input, allowing an attacker to inject malicious scripts that execute in the context of the victim's browser. This vulnerability can be exploited remotely without requiring authentication, though it does require user interaction to trigger the malicious payload (e.g., clicking a crafted link). The disclosed exploit enables attackers to perform actions such as session hijacking, defacement, or redirecting users to malicious sites, thereby compromising confidentiality and integrity of user sessions. The CVSS 4.0 base score is 5.1 (medium severity), reflecting the network attack vector, low attack complexity, no privileges required, but requiring user interaction and limited impact on confidentiality and integrity. No known exploits are currently active in the wild, but public disclosure increases the risk of exploitation.

For European organizations using Seeyon Zhiyuan OA Web Application System 8.1 SP2, this vulnerability poses a moderate risk. The OA system is typically used for internal office automation, document management, and workflow processes, which often contain sensitive corporate information. Exploitation could lead to unauthorized access to session tokens, enabling attackers to impersonate legitimate users, access confidential data, or perform unauthorized actions within the application. This could result in data breaches, disruption of business processes, and reputational damage. Given the medium severity and requirement for user interaction, the impact is significant but not critical. However, organizations with high-value targets or sensitive data processed through this system should consider the risk elevated. Additionally, since the vulnerability is remotely exploitable without authentication, it increases the attack surface, especially if the affected system is accessible from the internet or less secure internal networks.

To mitigate this vulnerability, European organizations should prioritize applying vendor patches or updates as soon as they become available. In the absence of an official patch, organizations should implement input validation and output encoding on the affected URL parameters to prevent script injection. Web Application Firewalls (WAFs) can be configured with custom rules to detect and block malicious payloads targeting the vulnerable date.jsp endpoint. User awareness training should emphasize caution when clicking on suspicious links, especially those received via email or messaging platforms. Network segmentation can limit exposure of the OA system to only trusted internal users. Additionally, monitoring logs for unusual activity or repeated access attempts to the vulnerable endpoint can help detect exploitation attempts early. Regular security assessments and penetration testing focused on web application vulnerabilities should be conducted to identify and remediate similar issues proactively.