CVE-2025-57880 is a medium-severity vulnerability identified in the Hallo Welt! GmbH BlueSpice software, specifically affecting versions 5 through 5.1.1 of the BlueSpiceWhoIsOnline extension. The vulnerability is classified under CWE-116, which pertains to improper encoding or escaping of output. This flaw allows for Cross-Site Scripting (XSS) attacks, where an attacker can inject malicious scripts into web pages viewed by other users. The vulnerability arises because the application fails to correctly encode or escape user-supplied data before rendering it in the browser, enabling attackers to execute arbitrary JavaScript code in the context of the victim's session. The CVSS 4.0 base score is 5.9 (medium), with vector metrics indicating network attack vector, low attack complexity, partial authentication required, user interaction needed, and high impact on confidentiality. The vulnerability does not affect availability or integrity significantly but poses a risk to confidentiality by potentially exposing sensitive information through session hijacking or data theft. No known exploits are currently reported in the wild, and no patches have been linked yet. The vulnerability was published on September 19, 2025, and remains a concern for organizations using the affected BlueSpice versions.

For European organizations, this vulnerability could lead to unauthorized disclosure of sensitive information, session hijacking, or unauthorized actions performed on behalf of legitimate users within the BlueSpice platform. BlueSpice is a popular enterprise wiki software used for knowledge management and collaboration, often containing proprietary or sensitive corporate data. Exploitation of this XSS vulnerability could allow attackers to steal authentication tokens, manipulate user sessions, or conduct phishing attacks within the trusted environment. This risk is particularly significant for organizations relying on BlueSpice for internal documentation, compliance records, or intellectual property management. The medium severity indicates that while the vulnerability is exploitable remotely with low complexity, it requires some level of authentication and user interaction, which somewhat limits the attack surface. However, in environments with many users and high-value data, the impact could be substantial, potentially leading to data breaches or reputational damage. Additionally, regulatory frameworks such as GDPR impose strict requirements on protecting personal and sensitive data, so exploitation could result in compliance violations and associated penalties.

To mitigate this vulnerability effectively, European organizations should: 1) Immediately assess their BlueSpice installations to identify if affected versions (5 through 5.1.1) of the BlueSpiceWhoIsOnline extension are in use. 2) Apply any available patches or updates from Hallo Welt! GmbH as soon as they are released; if no patches are currently available, consider disabling or removing the vulnerable extension temporarily to eliminate the attack vector. 3) Implement strict Content Security Policy (CSP) headers to restrict the execution of unauthorized scripts and reduce the impact of potential XSS attacks. 4) Conduct thorough input validation and output encoding on all user-supplied data within the BlueSpice environment, especially in custom extensions or templates, to prevent injection of malicious code. 5) Educate users about the risks of clicking on suspicious links or interacting with unexpected content within the wiki platform. 6) Monitor logs and user activity for signs of exploitation attempts, such as unusual session behavior or unexpected script execution. 7) Consider deploying Web Application Firewalls (WAF) with rules tailored to detect and block XSS payloads targeting BlueSpice. These steps go beyond generic advice by focusing on immediate risk reduction through configuration changes, user awareness, and proactive monitoring.