CVE-2025-54789 is a medium-severity vulnerability affecting the 'Files' module (cfiles) of the HumHub social collaboration platform, specifically versions 0.16.9 and earlier. The vulnerability is categorized under CWE-80, which involves improper neutralization of script-related HTML tags, commonly known as a Cross-Site Scripting (XSS) flaw. The issue arises in the File Move functionality, where insufficient input validation allows an attacker to inject arbitrary JavaScript code. When a user interacts with the affected functionality, the malicious script executes within the context of their browser session, potentially leading to session hijacking, unauthorized actions, or data theft. The vulnerability does not require authentication (PR:L indicates low privileges), but does require user interaction (UI:P), such as clicking a crafted link or performing a file move operation. The CVSS 4.0 score of 5.1 reflects a medium impact, with network attack vector (AV:N), low attack complexity (AC:L), and no privileges required (PR:L). The vulnerability affects confidentiality, integrity, and availability to a limited extent, primarily through client-side script execution. The issue is fixed in version 0.16.10 of the cfiles module. No known exploits are reported in the wild as of the publication date.

For European organizations using HumHub with the vulnerable cfiles module, this XSS vulnerability could lead to unauthorized execution of JavaScript in users' browsers. This may result in session hijacking, theft of sensitive information, or unauthorized actions performed on behalf of users. Since HumHub is often used for internal collaboration and file sharing, exploitation could compromise internal communications and data confidentiality. The impact is particularly significant for organizations with sensitive or regulated data, such as financial institutions, healthcare providers, and government agencies. Additionally, the vulnerability could be leveraged as a foothold for further attacks within the network if combined with social engineering or phishing campaigns. However, the requirement for user interaction and the medium severity score suggest that the risk is moderate and can be mitigated with appropriate controls.

European organizations should promptly upgrade the HumHub cfiles module to version 0.16.10 or later to remediate this vulnerability. In addition, implement strict Content Security Policy (CSP) headers to restrict the execution of unauthorized scripts in browsers. Employ input validation and output encoding on all user-supplied data within the application to prevent script injection. Conduct user awareness training to recognize and avoid suspicious links or file operations that could trigger XSS attacks. Monitor web application logs for unusual activity related to file operations. If upgrading immediately is not feasible, consider disabling the File Move functionality temporarily or restricting it to trusted users only. Regularly scan the application with automated security testing tools to detect similar vulnerabilities proactively.