I was able to create a script that allows the user to send a post request to https://blockshot.ch/upload with a base64 image and could upload any image not limited to Minecraft screenshots. A possible fix could be having the client send a rotating key of sorts to the web server.

https://blockshot.ch/O9cG

This is likely due to me temporarily disabling validation when the Auth servers last had issues and forgetting to renewable it. I will look into this today.

Thanks for being it to our attention.