Forgotten Name (web/misc, 160 solves, 72 points)

We forgot what our secret domain name was... We remember that it starts with 6a... Can you help me recover it?

Hint: the domain name is not bruteforcable

The solution

It was marked as an easy challenge and was mostly about asset discovery.

From the description we can read that the goal is to find a "forgotten" domain name that the challenge could run on. In all other challenges from this and last year one could notice that they are hosted on *.*.jctf.pro if they need access to the outside world. Searching on https://crt.sh/?q=jctf.pro we can notice there is indeed a domain called 6a7573744354467b633372545f6c34616b735f6f3070737d.web.jctf.pro (this probably could be also done with various available domain discovery tools). When we visit the page under that domain we see a simple html page:

OH! You found it! Thank you <3

Nothing more. The domain name is written in hex, after decoding the hex part we get the flag.

In [1]: '6a7573744354467b633372545f6c34616b735f6f3070737d'.decode('hex')
Out[1]: 'justCTF{c3rT_l4aks_o0ps}'

Original writeup (https://hackmd.io/@terjanq/justCTF2020-writeups#Forgotten-Name-webmisc-160-solves-72-points).