CSRF prevention by requiring a custom header in GET requests

[enisdenjo]

Implement a "CORS check guarantee" through a Yoga plugin. If you have CORS enabled, almost all requests coming from the browser will have a preflight request - however, some requests are deemed "simple" and don't make a preflight. One example of such a request is a good ol' GET request without any headers, this request can be marked as "simple" and have preflight CORS checks skipped therefore skipping the CORS check.

This attack can be mitigated by saying: "all GET requests must have a custom header set". This would force all clients to manipulate the headers of GET requests, marking them as "_not-_simple" and therefore always executing a preflight request.

Apollo does this when using the csrfPrevention = true option.