If you cannot perform a full upgrade due to legacy dependencies, apply the standalone hotfix:

If you’ve been trying to move data or upload documents and ran into the dreaded "Katsem File Upload" error, you aren't alone. Whether you're a developer or a casual user, this hang-up is usually caused by a few specific bottlenecks in server configuration or file permissions.

may have security protocols that restrict specific file extensions ( .exe , .php , etc.) or MIME types.

After making these changes, always restart your web server and clear your browser cache. Many users have reported that an aggressive browser cache was the silent culprit even after the patch was applied.

In October 2024, users began reporting a specific error pattern. When attempting to upload files larger than 2MB—or certain file types like PDF, DOCX, or ZIP—the upload bar would reach 99% and then hang, eventually throwing a generic 500 Internal Server Error or a 413 Request Entity Too Large .

What (e.g., 413, 500, Permission Denied) shows up in your browser console or server logs?

Run the following command on your server to set correct permissions: