CVE-2025-51396 is a stored cross-site scripting (XSS) vulnerability identified in Live Helper Chat version 4.60. This vulnerability arises from insufficient input sanitization in the Telegram Bot Username parameter, which allows an attacker to inject malicious scripts or HTML content that are then stored and subsequently executed in the context of users accessing the affected application. Stored XSS vulnerabilities are particularly dangerous because the malicious payload is permanently stored on the server side and delivered to multiple users, potentially leading to widespread exploitation. In this case, the attacker must have at least limited privileges (PR:L) and user interaction is required (UI:R), such as a user viewing the injected content, for the exploit to succeed. The vulnerability affects confidentiality and integrity by enabling script execution that could steal session tokens, perform actions on behalf of users, or manipulate displayed content. The CVSS 3.1 base score is 5.4 (medium severity), reflecting network attack vector (AV:N), low attack complexity (AC:L), partial privileges required (PR:L), user interaction required (UI:R), and a scope change (S:C) indicating that the vulnerability affects resources beyond the initially vulnerable component. There are no known exploits in the wild yet, and no patches have been published at the time of this report. The vulnerability is classified under CWE-79, which is the standard classification for cross-site scripting issues.

For European organizations using Live Helper Chat, especially those integrating Telegram bots for customer support or communication, this vulnerability poses a risk of unauthorized script execution within their web applications. Exploitation could lead to theft of sensitive user data, session hijacking, or manipulation of chat content, undermining user trust and potentially violating data protection regulations such as GDPR. The scope change in the CVSS vector suggests that the impact could extend beyond the immediate application, possibly affecting other integrated systems or user sessions. Given that Live Helper Chat is often used by customer service teams, exploitation could disrupt business operations and damage reputation. Furthermore, compromised chat interfaces could be leveraged for phishing or social engineering attacks targeting European users. Although no known exploits exist yet, the medium severity and ease of injection indicate that attackers may develop exploits rapidly once the vulnerability becomes widely known.

European organizations should proactively audit their Live Helper Chat deployments, particularly focusing on the Telegram Bot Username parameter. Immediate mitigation steps include implementing strict input validation and output encoding on all user-controllable fields to prevent script injection. Organizations should monitor official Live Helper Chat channels for patches or updates addressing this vulnerability and apply them promptly once available. In the interim, consider disabling or restricting the use of Telegram bot integrations if feasible. Employ Content Security Policy (CSP) headers to limit the execution of unauthorized scripts within the chat application context. Additionally, security teams should conduct regular security assessments and penetration tests focusing on XSS vulnerabilities in chat interfaces. User awareness training should emphasize caution when interacting with chat content, especially if unexpected or suspicious messages appear. Logging and monitoring for anomalous activities related to Telegram bot parameters can help detect attempted exploitation.