Ory Hydra uses a CSRF (Cross-Site Request Forgery) cookie as a security measure to protect against CSRF attacks. CSRF is an attack where a malicious site tricks a user's browser into sending unwanted requests to another site where the user is authenticated, potentially allowing unauthorized actions to be performed on behalf of the user. The CSRF cookie in Hydra is part of the synchronizer token pattern: when a form is rendered (such as during login or consent flows), a hidden input field containing a CSRF token is included. This token must match the value stored in the CSRF cookie. When the form is submitted, Hydra compares the submitted token with the cookie value. If they match, the request is considered legitimate; if not, the request is rejected. This mechanism ensures that only requests originating from the legitimate user interface are accepted, preventing malicious sites from forging requests on behalf of the user [Defenses against cross-site request forgery](https://www.ory.sh/docs/kratos/concepts/security#defenses-against-cross-site-request-forgery). In summary, Hydra's CSRF cookie protects against unauthorized actions initiated from other sites, ensuring that sensitive operations (like login and consent) can only be performed by the user through the intended UI.

@chilly-king-10285 But Hydra does not have a CSRF token value rendered in the form. Does that mean that the protection does not work?

Based on the available knowledge sources, Ory Hydra does use CSRF cookies for protection, but the documentation does not explicitly state that Hydra renders a CSRF token value in the form itself, as is common with the synchronizer token pattern used in Ory Kratos [Defenses against cross-site request forgery](https://www.ory.sh/docs/kratos/concepts/security#defenses-against-cross-site-request-forgery). The Hydra documentation and related guides focus on configuring cookie attributes (such as SameSite, domain, and secure flags) and mention CSRF cookies, but do not provide details about including a CSRF token in the form or how the token is validated on submission [Configuring cookies](https://www.ory.sh/docs/hydra/guides/cookies). There is also no explicit mention in the knowledge sources about the exact mechanism Hydra uses to validate CSRF tokens in forms. Therefore, if Hydra does not render a CSRF token in the form, it is unclear from the provided documentation how CSRF protection is enforced in those flows. The knowledge sources do not contain enough information to confirm whether the protection would still work or if there are alternative mechanisms in place. If you require a definitive answer about Hydra's CSRF protection mechanism in forms, you may need to consult the official Ory Hydra documentation or source code directly, as the current knowledge sources do not provide a clear answer.