Is owner of the server playing some tricks, when I tried that URL on Firefox Focus on my phone, it is just the text and I believe what parent wanted to submit, but indeed it looks fishy, I got 403 when tried to see what the redirect was using curl.
This is one reason I love having changed network.http.referer.XOriginPolicy[1] in Firefox. I never send the referer to third party domains, and I've only ever seen one or two sites broken because of this. It's a vast improvement for privacy as well.