Hatchet - Unauthenticated OAuth state CSRF / login-CSRF via empty-state collision in ValidateOAuthState

Summary

Hatchet version v0.86.26 and below is vulnerable to OAuth state CSRF (login CSRF / account fixation).

The vulnerable code clears the session oauth_state_<integration> value to the empty string "" after a successful OAuth callback rather than removing the key, and the subsequent state-equality check then accepts an empty ?state= parameter on any later callback request — allowing an unauthenticated attacker to bind an already-authenticated victim's session cookie to an attacker-controlled OAuth identity (account takeover via login-CSRF).

Impact

Affected configurations: any deployment that has enabled at least one of auth.google.enabled, auth.github.enabled, or the Slack integration, and where the victim has completed at least one OAuth flow on that integration in the current session. Bug present on main HEAD and in every tagged release up to and including v0.86.26 (commit 243f41d9e1161e70d47dfc0a6509f1c4ddfc9c23).