Python Social Auth is a social authentication/registration mechanism. Prior to version 5.0.0, the Vend OAuth2 backend used only the numeric Vend user_id as the social-auth UID. When multiple Vend shops authenticate through the same application, users from different shops with the same internal Vend user ID could collide in the social-auth association table. A user from one shop could then be authenticated as the local account previously associated with the same numeric user ID from another shop. The issue affects applications using the Vend OAuth2 backend with more than one Vend shop. Version 5.0.0 patches the issue.