Natas Level 4 -> Level 5

Skills: Cookie modification

Username: natas5 
Password: Z9tkRkWmpt9Qr7XrR5jWRkgOU901swEZ 
Target URL: http://natas5.natas.labs.overthewire.org

Using natas5 password, we login but we get "Access disallowed error".

Access Disallowed

Looking the request at BurpSuite, we see a long string of Cookie which is set to "loggedin=0"

Cookie is set to "loggedin=0"

By changing it to "1" manually, we get in!!!

Setting Cookie: "loggedin" to "1"

Access granted!!!