Found via Vanessa Jackman.
This is the "wpengine" admin user that our staff uses to gain access to your admin area to provide support and troubleshooting. It can only be accessed by a button in our secure log that auto generates a password and dumps that password after the staff member has logged in. We have taken extreme measures to ensure that our own user is not going to be misused to harm any of our clients sites. View all posts by wpengine