CVE-2025-6700 is a cross-site scripting (XSS) vulnerability identified in version 1.1.0 of the Xuxueli xxl-sso product, specifically within the /xxl-sso-server/login endpoint. The vulnerability arises from improper handling and sanitization of the 'errorMsg' parameter, which can be manipulated by an attacker to inject malicious scripts. This flaw allows an attacker to craft a specially crafted URL or request that, when processed by the vulnerable login page, executes arbitrary JavaScript in the context of the victim's browser session. The vulnerability is remotely exploitable without requiring authentication, and user interaction is necessary to trigger the malicious script execution (e.g., by clicking a malicious link). The CVSS v4.0 base score is 5.3, indicating a medium severity level. The vendor has been contacted but has not responded, and no official patch or mitigation has been released. Although no known exploits are currently observed in the wild, the public disclosure of the vulnerability increases the risk of exploitation by attackers. Xxl-sso is a single sign-on solution, and compromise of its login interface could lead to session hijacking, credential theft, or further attacks targeting authenticated sessions. The vulnerability affects confidentiality and integrity primarily through potential theft of session tokens or user credentials, and availability impact is minimal. The attack vector is network-based with low attack complexity and no privileges required, but user interaction is necessary to trigger the exploit. Given the nature of XSS, the risk is heightened in environments where users have elevated privileges or where sensitive data is accessible post-login.

For European organizations using xxl-sso 1.1.0, this vulnerability poses a moderate risk. Exploitation could lead to unauthorized access to user sessions, enabling attackers to impersonate legitimate users or steal sensitive information. This is particularly concerning for organizations relying on xxl-sso for centralized authentication across multiple internal or cloud services, as a successful attack could cascade into broader access compromises. The impact is amplified in sectors handling sensitive personal data, such as finance, healthcare, and government, due to potential GDPR implications and reputational damage. Additionally, the lack of vendor response and absence of patches increases exposure time. Attackers could leverage this vulnerability in targeted phishing campaigns to trick users into clicking malicious links, leading to session hijacking or credential theft. While the vulnerability does not directly affect system availability, the resulting breaches could disrupt business operations and lead to costly incident response and remediation efforts.

Given the absence of an official patch, European organizations should implement the following specific mitigations: 1) Employ web application firewalls (WAFs) with custom rules to detect and block malicious payloads targeting the 'errorMsg' parameter in the /xxl-sso-server/login endpoint. 2) Conduct input validation and output encoding on the server side if possible by applying temporary code-level fixes or wrappers to sanitize the 'errorMsg' parameter before rendering. 3) Educate users about phishing risks and encourage cautious behavior regarding unsolicited links, especially those pointing to authentication portals. 4) Monitor web server logs and application telemetry for unusual or suspicious requests containing script tags or encoded payloads in the 'errorMsg' parameter. 5) Isolate the xxl-sso service behind VPN or restrict access to trusted networks to reduce exposure. 6) Consider deploying Content Security Policy (CSP) headers to limit the execution of unauthorized scripts in browsers. 7) Plan for an upgrade or migration to a patched or alternative SSO solution once available. 8) Regularly review and update incident response plans to quickly address potential exploitation attempts.