CVE-2025-41349 is a stored Cross-site Scripting (XSS) vulnerability identified in version 24.11.27 of WinPlus, a product developed by Informática del Este. The vulnerability stems from improper neutralization of user-supplied input in the 'descripcion' parameter processed by the endpoint '/WinplusPortal/ws/sWinplus.svc/json/savesolpla_post'. Specifically, the application fails to adequately sanitize or encode this input before storing and subsequently rendering it in web pages. This flaw allows an authenticated attacker to craft a malicious POST request containing JavaScript payloads that get stored on the server. When other authenticated users access the affected pages, the malicious script executes in their browsers, potentially enabling session cookie theft, account hijacking, or other malicious actions within the victim's session context. The CVSS 4.0 vector indicates network attack vector (AV:N), low attack complexity (AC:L), no privileges required (PR:L - low privileges), and user interaction required (UI:P). The vulnerability does not affect confidentiality, integrity, or availability directly but compromises session security (SI:L). No patches or official fixes have been published yet, and no known exploits are reported in the wild. The vulnerability was reserved in April 2025 and published in November 2025, indicating recent discovery and disclosure. The CWE-79 classification confirms this is a classic stored XSS issue arising from improper input validation during web page generation.

For European organizations, this vulnerability poses a moderate risk primarily to confidentiality and user session integrity. Successful exploitation could lead to session hijacking, allowing attackers to impersonate legitimate users, access sensitive data, or perform unauthorized actions within the WinPlus application. This is particularly concerning for sectors handling sensitive or regulated data such as finance, healthcare, and government services. The requirement for authentication and user interaction reduces the likelihood of widespread automated exploitation but does not eliminate targeted attacks. Organizations relying on WinPlus 24.11.27 may face reputational damage, regulatory penalties under GDPR if personal data is compromised, and operational disruptions. The vulnerability could also be leveraged as a foothold for further lateral movement within networks. Given the absence of known exploits, proactive mitigation is critical to prevent future attacks.

1. Immediate mitigation should focus on implementing strict input validation and output encoding for the 'descripcion' parameter to neutralize malicious scripts before storage and rendering. 2. Deploy Web Application Firewalls (WAFs) with rules specifically targeting XSS payload patterns to detect and block malicious POST requests. 3. Enforce least privilege principles for user accounts to limit the impact of compromised sessions. 4. Conduct user awareness training emphasizing the risks of interacting with suspicious content and the importance of logging out after sessions. 5. Monitor application logs for unusual POST requests or repeated attempts to inject scripts. 6. Coordinate with Informática del Este for official patches or updates and apply them promptly once available. 7. Consider implementing Content Security Policy (CSP) headers to restrict script execution sources. 8. Regularly audit and test the application for similar input validation weaknesses to prevent future vulnerabilities.