CVE-2025-0209 is a reflected Cross-Site Scripting (XSS) vulnerability identified in WSO2 Identity Server version 7.0.0, specifically within the account registration flow. The root cause of this vulnerability is improper output encoding during web page generation, which allows an attacker to inject malicious JavaScript payloads that are reflected back in the server's HTTP response. When a victim interacts with a crafted URL or form input, the injected script executes in their browser context. This can lead to multiple malicious outcomes, including redirection to attacker-controlled websites, unauthorized modification of the user interface, and exfiltration of sensitive data accessible within the browser environment. Notably, session cookies are protected with the httpOnly flag, which prevents direct session hijacking via JavaScript, but other sensitive information or actions could still be compromised. The vulnerability has a CVSS 3.1 base score of 6.1, indicating a medium severity level. It requires no privileges and no authentication but does require user interaction (e.g., clicking a malicious link). The scope is changed, meaning the vulnerability affects components beyond the initially vulnerable module. Currently, there are no known exploits in the wild, and no official patches have been published yet. The CWE classification is CWE-79, which corresponds to improper neutralization of input during web page generation, a common vector for XSS attacks.

For European organizations using WSO2 Identity Server 7.0.0, this vulnerability poses a moderate risk primarily to the confidentiality and integrity of user interactions. Since WSO2 Identity Server is often used as a centralized identity and access management solution, exploitation could undermine trust in authentication flows, potentially enabling phishing or social engineering attacks by redirecting users to malicious sites. The ability to modify the user interface could also facilitate UI redressing or trick users into divulging credentials or sensitive data. Although session hijacking is mitigated by httpOnly cookies, attackers might still steal tokens or data accessible via JavaScript, impacting confidentiality. The reflected nature of the XSS means attacks require user interaction, limiting automated exploitation but still posing a risk in targeted phishing campaigns. Availability is not impacted. The medium severity suggests that while the threat is significant, it is not critical, but organizations relying heavily on WSO2 Identity Server for user authentication and registration should prioritize remediation to maintain security posture and user trust.

European organizations should implement the following specific mitigations: 1) Apply strict input validation and output encoding on all user-supplied data in the account registration flow to neutralize malicious scripts. 2) Employ Content Security Policy (CSP) headers to restrict the execution of unauthorized scripts and reduce the impact of potential XSS payloads. 3) Monitor and log unusual registration flow activities to detect potential exploitation attempts. 4) Educate users and administrators about phishing risks associated with malicious URLs exploiting this vulnerability. 5) Since no official patch is currently available, consider deploying a Web Application Firewall (WAF) with custom rules to detect and block reflected XSS payloads targeting the registration endpoint. 6) Plan for rapid deployment of official patches once released by WSO2. 7) Review and harden other identity server configurations to minimize attack surface, including limiting exposure of the registration endpoint to trusted networks where feasible.