The challange:
Access disallowed. You are not logged in

Solving it:
Reading the message, there probably is a cookie with a value of 1 of 0 which makes you logged in or not. Lets see in the developper console under the ‘storage’ tab. There is a cookie named ‘loggedin’ with the value of 0. Lets change this to 1 and refresh the page.

After changing the value to 1 and refreshing the page we are granted with the password of natas6.