Authlib is a Python library which builds OAuth and OpenID Connect servers. In version 1.6.5 and prior, cache-backed state/request-token storage is not tied to the initiating user session, so CSRF is possible for any attacker that has a valid state (easily obtainable via an attacker-initiated authentication flow). When a cache is supplied to the OAuth client registry, FrameworkIntegration.setstatedata writes the entire state blob under state{app}{state}, and getstate_data ignores the caller’s session altogether. This issue has been patched in version 1.6.6.