CVE-2025-63417 is a Stored Cross-Site Scripting (XSS) vulnerability identified in the chat functionality of the SelfBest platform version 2023.3. This vulnerability allows an authenticated attacker to inject arbitrary web scripts or HTML content into the chat message input field. Because the malicious content is stored on the server and subsequently rendered in the browsers of other users viewing the chat, it executes within their security context. The exploitation does not require user interaction beyond viewing the malicious message, and no privileges are needed to inject the payload, making it highly exploitable. The attack can lead to session hijacking, enabling attackers to steal session cookies, perform account takeover, or execute other client-side attacks such as keylogging or redirecting users to malicious sites. The CVSS 3.1 score of 7.2 reflects a high severity, with network attack vector, low attack complexity, no privileges required, no user interaction needed, and a scope change indicating that the vulnerability affects resources beyond the initially vulnerable component. The vulnerability is categorized under CWE-79, which is a common weakness related to improper neutralization of input during web page generation. Currently, no patches or official remediation guidance have been published, and no known exploits are reported in the wild. The vulnerability's presence in a chat system, a common vector for user interaction, increases the risk of widespread impact if exploited.

For European organizations using the SelfBest platform, this vulnerability poses a significant risk to confidentiality and integrity of user sessions and data. Attackers could hijack user sessions, leading to unauthorized access to sensitive information or systems. The stored nature of the XSS means that multiple users can be affected once a malicious message is posted, potentially amplifying the impact. This is particularly critical for organizations in sectors such as finance, healthcare, or government, where chat platforms may be used for sensitive communications. The lack of patches increases the window of exposure, and the ease of exploitation without user interaction or privileges heightens the threat. Additionally, exploitation could damage organizational reputation and lead to regulatory compliance issues under GDPR if personal data is compromised. The availability impact is low, but the integrity and confidentiality impacts are moderate to high.

Immediate mitigation should focus on implementing strict input validation and sanitization on the chat message input fields to prevent injection of malicious scripts. Employing output encoding or context-aware escaping when rendering chat messages in browsers is critical to neutralize any injected scripts. Organizations should consider deploying Content Security Policy (CSP) headers to restrict the execution of unauthorized scripts. Monitoring chat logs for suspicious messages and educating users about the risks can help detect and reduce exploitation. If possible, temporarily disabling or restricting chat functionality until a patch is available can reduce exposure. Vendors should be engaged to prioritize patch development and release. Additionally, applying web application firewalls (WAF) with rules targeting XSS payloads can provide an additional layer of defense. Regular security assessments and penetration testing focused on chat components are recommended to identify residual risks.