CVE-2025-66824 is a Stored Cross-Site Scripting (XSS) vulnerability identified in TrueConf Server version 5.5.2.10813. The vulnerability exists in the meeting_room parameter within the Meeting location field of the Create/Edit Conference feature. Due to improper sanitization of user-supplied input, attackers can inject malicious JavaScript payloads that are persistently stored on the server. When legitimate users visit the Conference Info page, the malicious script executes in their browsers under the context of the TrueConf Server domain. This execution can lead to full Account Takeover (ATO), enabling attackers to hijack user sessions, steal authentication tokens, and perform actions on behalf of the victim. The CVSS score of 7.3 (High) reflects the network attack vector, low attack complexity, requirement for low privileges, and user interaction. The vulnerability impacts confidentiality and integrity but does not affect availability. No public exploits or patches are currently available, increasing the urgency for organizations to implement interim mitigations. The flaw falls under CWE-79, a common web application security weakness related to improper neutralization of input. Given TrueConf Server's role in enterprise video conferencing, exploitation could disrupt secure communications and compromise sensitive organizational data.

For European organizations, this vulnerability poses a significant risk to the confidentiality and integrity of communications conducted via TrueConf Server. Successful exploitation can lead to account takeovers, allowing attackers to impersonate legitimate users, access sensitive meeting information, and potentially pivot to other internal systems. This is particularly critical for sectors relying on secure conferencing, such as government, finance, healthcare, and critical infrastructure. The persistent nature of the XSS increases the attack surface, as any user accessing the compromised Conference Info page may be affected. The lack of available patches and known exploits suggests a window of exposure, during which attackers could develop and deploy exploits. Additionally, the requirement for user interaction means phishing or social engineering could be used to lure victims to the malicious conference pages. The impact extends beyond individual users to organizational reputation and compliance with data protection regulations like GDPR, which mandate safeguarding personal data against unauthorized access.

European organizations should immediately audit their TrueConf Server deployments to identify affected versions, specifically v5.5.2.10813. Until a vendor patch is released, implement strict input validation and sanitization on the meeting_room parameter at the application or web server level, using web application firewalls (WAFs) with custom rules to detect and block suspicious payloads. Educate users about the risks of interacting with untrusted conference links and encourage vigilance against phishing attempts. Monitor server logs and user activity for anomalies indicative of exploitation attempts or account compromise. Restrict permissions for users who can create or edit conferences to minimize exposure. Consider isolating the conferencing platform within segmented network zones to limit lateral movement in case of compromise. Once TrueConf releases a security update, prioritize its deployment and verify remediation through penetration testing. Additionally, implement Content Security Policy (CSP) headers to reduce the impact of XSS attacks by restricting script execution contexts.