The Temporary Login Without Password WordPress plugin before 1.9.9 does not verify that the user requesting a temporary login holds network super admin rights before granting the new account those rights, allowing an administrator of a single site on a multisite network to take over the whole network. The same missing check also allows an existing account, including the attacker's own, to be promoted.
https://wpscan.com/vulnerability/09308b99-3142-44f0-b2e1-9f4680325d2d/