CVE-2025-53543 is a stored Cross-site Scripting (XSS) vulnerability identified in the Kestra event-driven orchestration platform, specifically affecting versions prior to 0.22.0. The vulnerability arises from improper neutralization of input during web page generation, classified under CWE-79. It manifests in the 'Overview' tab of the execution interface, where error messages display HTTP response data without adequate sanitization. This flaw allows an attacker with high privileges (as indicated by the CVSS vector requiring PR:H) and requiring user interaction (UI:R) to inject malicious scripts that are stored and later executed in the context of other users viewing the error messages. The vulnerability impacts confidentiality by potentially exposing sensitive information through script execution, though it does not affect integrity or availability directly. The CVSS score of 4.2 (medium severity) reflects the limited attack surface due to the need for authenticated high-privilege access and user interaction, as well as the local attack vector. No known exploits are currently reported in the wild, and the issue has been addressed in Kestra version 0.22.0.

For European organizations utilizing Kestra for orchestration and workflow automation, this vulnerability poses a moderate risk. Attackers with high-level access could exploit the stored XSS to execute malicious scripts within the administrative or operational interfaces, potentially leading to unauthorized disclosure of sensitive orchestration data or session hijacking. While the vulnerability does not directly compromise system integrity or availability, the confidentiality breach could facilitate further attacks or data leakage. Given Kestra's role in automating critical workflows, exploitation could disrupt trust in operational processes. European entities in sectors such as finance, manufacturing, or critical infrastructure that rely on Kestra may face compliance and reputational risks if this vulnerability is exploited. However, the requirement for authenticated high-privilege access and user interaction limits the likelihood of widespread exploitation.

To mitigate this vulnerability, European organizations should promptly upgrade Kestra to version 0.22.0 or later, where the issue is resolved. Until the upgrade is applied, organizations should restrict access to the Kestra interface to trusted administrators only, enforce strong authentication mechanisms, and monitor for unusual activity in the execution 'Overview' tab. Implementing Content Security Policy (CSP) headers can help reduce the impact of potential XSS by restricting script execution sources. Additionally, security teams should conduct regular code reviews and penetration testing focused on web interface components to detect similar input validation issues. Logging and alerting on anomalous HTTP responses or script injections in the orchestration platform can provide early detection of exploitation attempts. Finally, educating privileged users about the risks of interacting with untrusted content in the interface can reduce the chance of successful exploitation.