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. Here are a couple of recommendations for Windows:
FileZilla — an excellent cross-platform, Open Source client for various protocols including SFTP