Whenever I ask someone to upload a sample file, I prefer the upload is done to my own server. It is only reachable via SFTP (SSH file transfer protocol).
Please place the file(s) in the folder named "upload". If you're uploading more than one file, please create a separate folder for that and name it sensibly, e.g. include your name or the bug number you're referring to. Thanks.
There are several Open Source SFTP clients for all operating systems out there. Linux and macOS come with the command-line utility "sftp" included. For Windows I suggest WinSCP, a small but powerful Open Source program capable of using all modern features of SSH/SFTP.
Note: You can only upload to this server, not download from it. Stop trying!
The login data is as follows:
Host name: ftp.bunkus.org
Port number: 2222
File protocol: "SFTP" (for command line users: use the sftp command, not scp)