Uix UserCenter <= 1.0.3 - Unauthenticated Privilege Escalation

The Uix UserCenter WordPress plugin through 1.0.3 does not verify that the account being modified through an unauthenticated profile-update action belongs to the requester, and it authenticates that action with a token whose signing key is hardcoded and identical across every install, allowing unauthenticated attackers to forge a token for any user, overwrite an administrator's email and password, and take over the account.