CVE-2025-5770 is a reflected cross-site scripting (XSS) vulnerability identified in multiple versions of WSO2 Identity Server (6.0.0, 6.1.0, 7.0.0, and 7.1.0). The root cause is improper neutralization of input during web page generation, specifically a lack of output encoding in the authentication endpoints. This flaw allows an attacker to craft malicious URLs or inputs that inject arbitrary JavaScript code, which the server reflects back in its HTTP responses. When a victim user interacts with such a crafted link or input, the malicious script executes in their browser context. Potential consequences include redirection to attacker-controlled websites, manipulation of the user interface to deceive users, or unauthorized access to sensitive information accessible via the browser. The vulnerability does not enable direct session hijacking because session cookies are marked with the httpOnly flag, preventing JavaScript access. The CVSS 3.1 base score is 6.1, reflecting a medium severity level, with attack vector network-based, low attack complexity, no privileges required, user interaction required, and a scope change indicating impact beyond the vulnerable component. No public exploits have been reported yet, but the vulnerability's presence in widely used authentication infrastructure makes it a significant concern. The lack of official patches at the time of reporting necessitates immediate attention to mitigation strategies.

For European organizations, the impact of CVE-2025-5770 can be significant, especially for those relying on WSO2 Identity Server for critical authentication and identity management services. Successful exploitation could lead to compromised user trust due to phishing or redirection attacks, potential leakage of sensitive information accessible via the browser, and manipulation of authentication workflows. Although session hijacking is mitigated by httpOnly cookies, attackers could still perform actions such as stealing tokens stored in browser storage or manipulating UI elements to capture credentials or other sensitive inputs. This can result in unauthorized access to internal systems or data breaches. The vulnerability could also facilitate social engineering attacks, increasing the risk of broader compromise. Given the widespread adoption of WSO2 products in sectors like finance, government, and telecommunications across Europe, the threat could disrupt critical services and damage organizational reputations. The medium severity score suggests moderate risk, but the scope of affected systems and potential for user-targeted attacks elevate the importance of timely remediation.

European organizations should implement the following specific mitigations: 1) Monitor WSO2 official channels for patches addressing CVE-2025-5770 and apply them promptly once available. 2) In the interim, implement web application firewall (WAF) rules to detect and block suspicious input patterns targeting authentication endpoints, focusing on script injection attempts. 3) Employ Content Security Policy (CSP) headers to restrict the execution of unauthorized scripts in browsers, reducing the impact of reflected XSS. 4) Conduct security reviews and code audits of any customizations or integrations with WSO2 Identity Server to ensure proper output encoding and input validation. 5) Educate users about the risks of clicking on suspicious links, especially those related to authentication workflows. 6) Use multi-factor authentication (MFA) to reduce the risk of unauthorized access even if credential theft occurs. 7) Log and monitor authentication endpoint access for anomalous patterns indicative of exploitation attempts. 8) Consider isolating or segmenting identity management infrastructure to limit lateral movement in case of compromise. These measures collectively reduce the risk and impact of exploitation while awaiting official patches.