Medium · published October 15, 2026
Python Social Auth is a social authentication/registration mechanism. Prior to 5.0.2, the LINE backend exchanges an authorization code without validating the returned OAuth state. An attacker can begin authorization for an attacker-controlled LINE account and induce a victim to visit the resulting callback URL, causing the application to log the victim into the attacker's account. When account linking is enabled, the same missing validation can link the attacker's LINE identity to the victim's existing account and create a persistent unauthorized login path. Only applications with the LINE backend enabled are affected. This issue is fixed in version 5.0.2.