CVE-2025-57900 is a Stored Cross-site Scripting (XSS) vulnerability classified under CWE-79, affecting the Ataur R GutenKit software up to version 2.4.2. The vulnerability arises from improper neutralization of input during web page generation, allowing malicious input to be stored and later executed in the context of a victim's browser. This type of vulnerability typically occurs when user-supplied data is embedded in web pages without adequate sanitization or encoding, enabling attackers to inject arbitrary scripts. The CVSS 3.1 base score of 6.5 reflects a medium severity, with the vector indicating network attack vector (AV:N), low attack complexity (AC:L), requiring privileges (PR:L), user interaction (UI:R), scope changed (S:C), and low impact on confidentiality, integrity, and availability (C:L/I:L/A:L). The scope change means the vulnerability can affect resources beyond the initially vulnerable component, potentially impacting other parts of the system or user sessions. Exploitation requires an attacker to have some level of privileges on the system and to trick a user into interacting with the malicious payload, such as by clicking a crafted link or viewing a compromised page. Although no known exploits are currently reported in the wild, the presence of stored XSS can lead to session hijacking, credential theft, defacement, or distribution of malware, especially if combined with social engineering. The lack of available patches at the time of publication suggests that affected organizations should prioritize mitigation and monitoring. GutenKit is a product developed by Ataur R, and the vulnerability affects all versions up to 2.4.2, with no specific earliest affected version identified. Stored XSS vulnerabilities are particularly dangerous because the malicious script is persistently stored on the server and served to multiple users, increasing the attack surface and potential impact.

For European organizations using GutenKit, this vulnerability poses a risk of client-side attacks that can compromise user sessions, steal sensitive information, or facilitate further attacks such as privilege escalation or lateral movement within networks. Given the medium severity and requirement for some privileges and user interaction, the threat is moderate but should not be underestimated. Organizations in sectors with high regulatory scrutiny, such as finance, healthcare, and government, may face additional compliance risks if user data confidentiality or integrity is compromised. The stored nature of the XSS means that multiple users can be affected once the malicious payload is injected, potentially leading to widespread impact within an organization or its customer base. Additionally, the scope change indicates that the vulnerability could affect components beyond the immediate application, possibly impacting integrated systems or services. The absence of known exploits in the wild reduces immediate risk but does not eliminate the threat, as attackers may develop exploits once the vulnerability details are public. European organizations should consider the reputational damage and legal consequences of data breaches resulting from exploitation of this vulnerability.

1. Immediate mitigation should include implementing strict input validation and output encoding on all user-supplied data within GutenKit, especially in areas where data is stored and later rendered in web pages. 2. Employ Content Security Policy (CSP) headers to restrict the execution of unauthorized scripts in browsers, limiting the impact of potential XSS payloads. 3. Conduct thorough code reviews and security testing focusing on input handling and sanitization mechanisms within GutenKit. 4. Monitor application logs and user reports for unusual activity or indications of attempted XSS exploitation. 5. Restrict privileges to the minimum necessary to reduce the risk posed by attackers needing some level of access to exploit the vulnerability. 6. Educate users about the risks of interacting with suspicious links or content, as user interaction is required for exploitation. 7. Engage with the vendor or community to obtain patches or updates as soon as they become available, and plan for timely deployment. 8. Consider deploying web application firewalls (WAFs) with rules tailored to detect and block XSS payloads targeting GutenKit. 9. Isolate critical systems using GutenKit from less trusted networks to reduce exposure. 10. Regularly update and patch all related software components to minimize the attack surface.