CVE-2025-56515 is a file upload vulnerability identified in the Fiora chat application version 1.0.0, specifically within the user avatar upload functionality. The vulnerability arises because the application does not properly validate the content of uploaded SVG (Scalable Vector Graphics) files. Attackers can exploit this by uploading malicious SVG files that embed foreignObject elements containing iframe tags and JavaScript event handlers such as 'onmouseover'. When these SVG files are rendered in the context of user profiles, the embedded JavaScript executes in the victim's browser. This execution can lead to session hijacking, cookie theft, and unauthorized actions performed with the privileges of the affected user. The vulnerability leverages the ability of SVG files to contain active content, which is often overlooked in file upload sanitization processes. Although no known exploits are currently reported in the wild, the nature of the vulnerability makes it a significant risk, especially in environments where user-generated content is displayed without sufficient sanitization or content security policies. The lack of a CVSS score indicates that the vulnerability is newly published and has not yet been fully assessed or exploited. However, the technical details suggest a high-risk cross-site scripting (XSS) vector via SVG files, which is a common and impactful attack vector in web applications.

For European organizations, the impact of this vulnerability can be substantial, particularly for those using the Fiora chat application or similar platforms that allow user avatar uploads with SVG support. Successful exploitation could lead to compromise of user sessions, enabling attackers to impersonate users, access sensitive information, and perform unauthorized actions within the application. This could result in data breaches, loss of user trust, and potential regulatory penalties under GDPR due to inadequate protection of personal data. Additionally, the ability to execute arbitrary JavaScript could facilitate further attacks such as phishing, malware distribution, or lateral movement within corporate networks. Organizations relying on Fiora chat for internal communications or customer interactions may face operational disruptions and reputational damage. The vulnerability's exploitation does not require user authentication to upload the malicious SVG, but victim interaction is needed to trigger the payload by viewing the affected profile, which broadens the attack surface in collaborative or social environments.

To mitigate this vulnerability, European organizations should implement strict server-side validation and sanitization of SVG files uploaded as avatars. This includes disallowing or stripping potentially dangerous elements such as foreignObject, iframe tags, and JavaScript event handlers within SVG content. Employing a whitelist approach for allowed SVG elements and attributes is recommended. Additionally, organizations should enforce Content Security Policy (CSP) headers that restrict script execution and iframe embedding to trusted sources, reducing the risk of malicious script execution. Updating or patching the Fiora chat application once a vendor fix is available is critical. In the interim, disabling SVG uploads or restricting avatar uploads to safer image formats (e.g., PNG, JPEG) can reduce exposure. User education about the risks of interacting with untrusted profiles and monitoring application logs for suspicious upload activity are also advisable. Finally, integrating web application firewalls (WAFs) with rules targeting SVG-based XSS attempts can provide an additional layer of defense.