Site configured improperly at subdomain of lyst.co.uk

How it was found

Steps to reproduce the issue:

Go to : "https://w.lyst.co.uk/"

It will give you message

The owner of w.lyst.co.uk has configured their website improperly.
To protect your information from being stolen, 
Firefox has not connected to this website.

Image: {F163225} A attacker will send this link to user, where he will be shown this message, will break her/his trust from lyst.

Tested in Firefox latest version.

Thanks