CVE-2025-41350 is a stored Cross-site Scripting (XSS) vulnerability identified in version 24.11.27 of WinPlus, a software product developed by Informática del Este. The vulnerability stems from improper neutralization of user input during web page generation, specifically in the handling of the 'descripcion' parameter submitted via POST requests to the '/WinplusPortal/ws/sWinplus.svc/json/savesoldoc_post' endpoint. Because the input is not properly sanitized or validated, malicious scripts can be injected and stored on the server. When an authenticated user later accesses the affected page or functionality, the malicious script executes in their browser context. This can lead to theft of session cookies, enabling attackers to hijack user sessions and potentially escalate privileges or access sensitive data. The vulnerability requires the attacker to have low privileges (PR:L) and user interaction (UI:P), meaning the victim must interact with the malicious content for exploitation. The CVSS 4.0 vector indicates network attack vector (AV:N), low attack complexity (AC:L), no privileges required (AT:N), and partial scope impact (S:I), with no impact on confidentiality, integrity, or availability directly (VC:N/VI:N/VA:N). No known exploits are currently reported in the wild, but the vulnerability is publicly disclosed and should be addressed promptly. The lack of a patch link suggests that a fix may not yet be available, increasing the urgency for mitigation.

For European organizations using WinPlus 24.11.27, this vulnerability poses a risk of session hijacking through stored XSS attacks. Attackers can exploit this flaw to steal authenticated users' session cookies, potentially gaining unauthorized access to sensitive systems or data. This is particularly concerning for organizations handling critical or sensitive information, such as financial institutions, healthcare providers, and government agencies. The medium severity rating reflects that while the vulnerability does not directly compromise system integrity or availability, the confidentiality of user sessions and data can be undermined. Exploitation requires user interaction and some level of authentication, which somewhat limits the attack surface but does not eliminate risk. The absence of known exploits in the wild currently reduces immediate threat but does not preclude future exploitation. Given the potential for lateral movement or privilege escalation following session hijacking, the impact on operational security and compliance with data protection regulations (e.g., GDPR) can be significant.

European organizations should implement the following specific mitigations: 1) Apply any available patches or updates from Informática del Este as soon as they are released. 2) If patches are not yet available, implement strict input validation and output encoding on the 'descripcion' parameter at the application or web server level to neutralize malicious scripts. 3) Employ Web Application Firewalls (WAFs) with custom rules to detect and block suspicious payloads targeting the vulnerable endpoint. 4) Enforce secure cookie attributes such as HttpOnly and Secure flags to reduce the risk of cookie theft via XSS. 5) Conduct user awareness training to recognize and avoid interacting with suspicious links or content. 6) Monitor logs and network traffic for unusual POST requests or access patterns to '/WinplusPortal/ws/sWinplus.svc/json/savesoldoc_post'. 7) Consider implementing Content Security Policy (CSP) headers to restrict script execution contexts. 8) Review and limit user privileges to minimize the impact of compromised sessions. These measures collectively reduce the likelihood and impact of exploitation until a vendor patch is available.