The vulnerability chain involves three key points: 1) The auth request creation endpoint (post_auth_request) initially didn't validate device ownership, allowing attackers to create requests for any user. 2) The login flow (_password_login) didn't verify auth_request-user association, enabling request misuse. 3) Auth request retrieval (get_auth_request) had insufficient access controls. The high confidence comes from direct evidence in commit diffs showing security checks were added to these functions, and the CVE description matches these attack vectors. The medium confidence for get_auth_request stems from its role in potential information disclosure that could aid impersonation attacks.