CVE-2025-61681 is a medium-severity stored Cross-site Scripting (XSS) vulnerability affecting KUNO CMS, a full-stack blog application developed by xuemian168. Versions prior to 1.3.14 improperly validate file uploads by relying solely on the Content-Type HTTP header to determine file type. This insufficient validation allows attackers to upload SVG files containing embedded malicious JavaScript code, disguised as image files. Since the application does not perform content analysis or enforce a whitelist of allowed file extensions, these malicious SVG files are accepted and stored on the server. When legitimate users access pages displaying these uploaded SVGs, the embedded JavaScript executes in their browsers, leading to arbitrary script execution. This can result in theft of user credentials, session hijacking, or other malicious actions within the context of the victim's browser session. The vulnerability is classified under CWE-79 (Improper Neutralization of Input During Web Page Generation) and CWE-434 (Unrestricted Upload of File with Dangerous Type). Exploitation requires no authentication but does require user interaction to trigger the malicious script. The vulnerability was publicly disclosed on October 3, 2025, and fixed in version 1.3.14 of KUNO CMS. No known exploits are currently reported in the wild. The CVSS v3.1 base score is 5.4, reflecting network attack vector, low attack complexity, no privileges required, user interaction required, and limited impact on confidentiality and integrity without availability impact.

For European organizations using KUNO CMS versions prior to 1.3.14, this vulnerability poses a risk of client-side script execution leading to potential theft of user credentials, session tokens, or unauthorized actions performed on behalf of users. This can compromise the confidentiality and integrity of user data and may facilitate further attacks such as phishing or lateral movement within the organization. Since KUNO CMS is a blogging platform, public-facing websites could be used as attack vectors to target employees or customers. The impact is particularly significant for organizations that rely on KUNO CMS for customer engagement or internal communication, as trust and data privacy could be undermined. Additionally, regulatory frameworks like GDPR impose strict requirements on protecting personal data, and exploitation of this vulnerability could lead to compliance violations and reputational damage. However, the lack of known active exploits and the medium severity score suggest that the immediate risk is moderate but should not be underestimated.

European organizations should immediately upgrade KUNO CMS to version 1.3.14 or later to apply the official patch. Until the upgrade is performed, implement strict server-side validation of uploaded files beyond Content-Type headers, including: 1) Enforce a whitelist of allowed file extensions, explicitly excluding SVG or other potentially dangerous formats. 2) Perform content inspection of uploaded files to detect and block files containing embedded scripts or suspicious content. 3) Configure web application firewalls (WAFs) to detect and block malicious SVG payloads and suspicious upload patterns. 4) Limit file upload permissions to authenticated and authorized users only, if possible. 5) Implement Content Security Policy (CSP) headers to restrict execution of inline scripts and reduce the impact of XSS attacks. 6) Educate users about the risks of interacting with untrusted content and encourage cautious behavior. Regularly audit and monitor uploaded content for anomalies. These measures combined will reduce the attack surface and mitigate exploitation risk until the patch is applied.