Jirafeau normally prevents browser preview for text files due to the possibility that for example SVG and HTML documents could be exploited for cross site scripting. This was done by storing the MIME type of a file and allowing only browser preview for MIME types beginning with image (except for image/svg+xml, see CVE-2022-30110, CVE-2024-12326 and CVE-2025-7066), video and audio. However, it was possible to bypass this check by sending a manipulated HTTP request with an invalid MIME type like image. When doing the preview, the browser tries to automatically detect the MIME type resulting in detecting SVG and possibly executing JavaScript code. To prevent this, MIME sniffing is disabled by sending the HTTP header X-Content-Type-Options: nosniff.