CVE-2025-66823 is an HTML Injection vulnerability identified in TrueConf server version 5.5.2.10813, specifically within the conference description field of the Create/Edit conference functionality. This vulnerability allows an attacker with authenticated access and privileges to create or modify conference details to inject arbitrary HTML code. When a victim subsequently accesses the Conference Info page, the injected HTML payload is executed in their browser context. Unlike classic Cross-Site Scripting (XSS), this vulnerability is classified as HTML Injection because it involves injecting HTML content rather than script code, but it can still be leveraged for UI manipulation, phishing, or social engineering attacks. The attack vector requires network access to the TrueConf server and valid user credentials with conference editing rights, as well as user interaction to view the compromised conference info page. The CVSS 3.1 base score of 3.5 reflects a low severity due to the limited impact on confidentiality and availability, the need for authentication, and user interaction. There is no indication of known exploits in the wild, and no patches or updates have been explicitly linked yet. The vulnerability falls under CWE-79, highlighting improper input sanitization or output encoding during web page generation. Organizations using TrueConf server for video conferencing should consider this vulnerability in their risk assessments and apply appropriate mitigations.

For European organizations, the primary impact of this vulnerability lies in the potential manipulation of conference information displayed to users, which could be exploited for social engineering or phishing attacks within the corporate environment. Although it does not directly compromise confidentiality or availability, the integrity of displayed content can be undermined, potentially leading to misinformation or user deception. Organizations relying on TrueConf for internal or external communications may face reputational risks if attackers exploit this flaw to inject misleading or malicious content. The requirement for authenticated access limits the attack surface to insiders or compromised accounts, but this does not eliminate risk, especially in large organizations with many users. The vulnerability could also be used as a stepping stone for more complex attacks if combined with other vulnerabilities or social engineering tactics. Given the widespread adoption of video conferencing tools in Europe, especially in sectors like finance, government, and healthcare, the vulnerability could have moderate operational impact if exploited.

To mitigate CVE-2025-66823, European organizations should first verify if they are running TrueConf server version 5.5.2.10813 or earlier and monitor vendor communications for official patches or updates. In the absence of a patch, organizations should restrict conference creation and editing privileges to trusted users only, minimizing the number of accounts that can inject HTML content. Implement strict input validation and output encoding on the conference description field to neutralize HTML tags and attributes, preventing injection. Additionally, educate users to be cautious when viewing conference info pages, especially if unexpected content appears. Network segmentation and access controls can limit exposure of the TrueConf server to internal trusted networks only. Regularly audit conference descriptions for suspicious content and monitor logs for unusual editing activity. Employ web application firewalls (WAFs) with custom rules to detect and block HTML injection attempts targeting the conference description field. Finally, incorporate this vulnerability into security awareness training to reduce the risk of social engineering attacks leveraging injected content.