CVE-2025-4294 is a Cross-Site Scripting (XSS) vulnerability classified under CWE-79, affecting the HotelRunner B2B platform versions prior to 04.06.2025. The vulnerability arises due to improper neutralization of input during web page generation, allowing malicious actors to inject and execute arbitrary scripts within the context of the affected web application. This flaw can be exploited remotely over the network without requiring physical access, but it requires the attacker to have some level of privileges (PR:H) and user interaction (UI:R), such as tricking an authenticated user into clicking a crafted link or submitting malicious input. The vulnerability has a CVSS v3.1 base score of 4.8, indicating a medium severity level. The vector string (AV:N/AC:L/PR:H/UI:R/S:C/C:L/I:L/A:N) reveals that while the attack complexity is low and no physical access is needed, the attacker must have high privileges and user interaction is necessary. The scope is changed (S:C), meaning the vulnerability affects resources beyond the initially vulnerable component. The impact affects confidentiality and integrity to a limited extent (C:L/I:L), but availability is not impacted (A:N). No known exploits are currently reported in the wild, and no patches or mitigation links have been published yet. The vulnerability could allow attackers to steal sensitive information, hijack user sessions, or perform unauthorized actions within the B2B platform, potentially compromising business operations and customer data confidentiality.

For European organizations using HotelRunner B2B, this vulnerability poses a risk primarily to the confidentiality and integrity of their data and user sessions. Given that HotelRunner B2B is a platform used in the hospitality industry for business-to-business interactions, exploitation could lead to unauthorized access to booking information, customer data, and internal communications. This could result in data breaches, reputational damage, and regulatory non-compliance under GDPR. The requirement for high privileges and user interaction somewhat limits the attack surface but does not eliminate risk, especially if insider threats or phishing campaigns are considered. The scope change indicates that the impact could extend beyond the immediate vulnerable component, potentially affecting other integrated systems or services. European hospitality businesses relying on this platform could face operational disruptions and loss of customer trust if the vulnerability is exploited.

1. Immediate implementation of strict input validation and output encoding on all user-supplied data within the HotelRunner B2B platform to prevent script injection. 2. Employ Content Security Policy (CSP) headers to restrict the execution of unauthorized scripts and reduce the impact of any injected code. 3. Conduct thorough code reviews and penetration testing focused on XSS vectors, especially in areas handling user input and dynamic content generation. 4. Limit user privileges strictly to the minimum necessary to reduce the risk posed by high-privilege accounts. 5. Educate users on phishing and social engineering risks to minimize successful user interaction exploitation. 6. Monitor logs for suspicious activities indicative of XSS exploitation attempts. 7. Coordinate with HotelRunner for timely patch releases and apply updates as soon as they become available. 8. Consider deploying Web Application Firewalls (WAF) with custom rules to detect and block XSS payloads targeting the platform.