CVE-2026-24399 is a critical security vulnerability classified under CWE-79 (Improper Neutralization of Input During Web Page Generation), commonly known as cross-site scripting (XSS). It affects chattermate.chat, a no-code AI chatbot agent framework, specifically versions 1.0.8 and earlier. The vulnerability arises because the chatbot accepts and executes malicious HTML and JavaScript payloads supplied as chat input without proper sanitization or neutralization. Attackers can craft an iframe element containing a javascript: URI, which when processed by the victim’s browser, executes arbitrary JavaScript code in the context of the web application. This execution context allows attackers to access sensitive client-side data such as localStorage tokens and cookies, which can be used for session hijacking, impersonation, or further attacks on the user. The vulnerability requires user interaction (the victim must view or interact with the malicious chat input) but does not require authentication or elevated privileges. The CVSS v3.1 score is 9.3 (critical), reflecting the high impact on confidentiality and integrity, ease of exploitation over the network, and the scope affecting user sessions. Although no known exploits are currently reported in the wild, the flaw poses a significant risk due to the nature of the data exposed and the widespread use of chatbots in customer service and internal communications. The issue was addressed and fixed in chattermate.chat version 1.0.9 by implementing proper input validation and sanitization to neutralize malicious payloads before rendering.

For European organizations, this vulnerability can lead to severe data breaches involving theft of session tokens and cookies, enabling attackers to impersonate users and gain unauthorized access to sensitive information or internal systems. Organizations relying on chattermate.chat for customer interaction or internal AI chatbot services risk exposure of confidential client data and internal communications. The compromise of user sessions can facilitate lateral movement within networks, leading to broader security incidents. Additionally, the reputational damage and regulatory consequences under GDPR for failing to protect personal data could be substantial. The attack vector requires user interaction, which may be exploited through social engineering or phishing campaigns targeting employees or customers. Given the critical severity and ease of exploitation, organizations must prioritize remediation to prevent potential exploitation and data loss.

1. Immediate upgrade to chattermate.chat version 1.0.9 or later, where the vulnerability is fixed. 2. Implement strict input validation and output encoding on all user-supplied content, especially chat inputs, to prevent injection of malicious HTML or JavaScript. 3. Employ Content Security Policy (CSP) headers to restrict execution of unauthorized scripts and iframe sources. 4. Conduct user awareness training to recognize and avoid interacting with suspicious chat inputs or links. 5. Monitor chat logs and user activity for signs of exploitation or anomalous behavior. 6. Use web application firewalls (WAFs) with rules tailored to detect and block XSS payloads targeting chattermate.chat. 7. Regularly audit and test chatbot implementations for security weaknesses, including penetration testing focused on injection flaws. 8. Isolate chatbot services from critical internal systems to limit potential lateral movement if compromised.