The Welcart e-Commerce WordPress plugin before 2.12.1 does not regenerate the session identifier on authentication and sets the session identifier from a user-supplied request parameter, allowing an unauthenticated attacker to fixate a shop member's session and take over their customer account after the victim logs in through an attacker-crafted request.
https://wpscan.com/vulnerability/3b2d4e7f-1e2a-4712-af9b-50080106d52c/