Review CSRF security

[crisward]

Not so much an issue, as something I will try to do.

The below article recommends checking specific headers between the request response cycle, as well as other considerations to further improve security. I'll see if I use this info to improve this shard.

https://www.owasp.org/index.php/Cross-Site_Request_Forgery_(CSRF)_Prevention_Cheat_Sheet