CVE-2025-56515: 
JavaScript vulnerability analysis and mitigation

A file upload vulnerability has been discovered in Fiora chat application version 1.0.0 (CVE-2025-56515). The vulnerability exists in the user avatar upload functionality, where the application fails to properly validate SVG file content. This security issue was disclosed on October 1, 2025, affecting the chat application developed by suisuijiang (Fiora GitHub).

The vulnerability stems from improper validation of SVG file content in the user avatar upload functionality. The application allows malicious SVG files containing embedded foreignObject elements with iframe tags and JavaScript event handlers (onmouseover) to be uploaded and stored. The vulnerability has received a CVSS v3.1 base score of 8.8 (HIGH) with the vector string CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H. The issue has been classified under CWE-79 (Improper Neutralization of Input During Web Page Generation) and CWE-434 (Unrestricted Upload of File with Dangerous Type) (NVD).

When rendered, the malicious SVG files can execute arbitrary JavaScript code, enabling attackers to steal user sessions, cookies, and perform unauthorized actions in the context of users viewing affected profiles. The vulnerability can lead to significant security breaches, potentially compromising user data and system integrity (GitHub POC).