GET aHEAD

We are given a website that shows two background colors:

The red button uses a GET request and the blue one uses a POST request. We do not see anything.

Since the challenge name includes HEAD, let’s see if we can perform a HEAD request using curl:

$ curl -I mercury.picoctf.net:47967
HTTP/1.1 200 OK
flag: picoCTF{r3j3ct_th3_du4l1ty_cca66bd3}  
Content-type: text/html; charset=UTF-8