When we intercept the request of 
http://20yjtzrx50hpypicbajmro9dy.ctf.p0wnhub.com:8888/
We see that it is redirecting to firebase host related to HZVIII which is:
```hzviii.firebaseio.com```
and when we search on internet we can get some information about misconfiguration in firebaseswhich appears in ".json" so we proceed the request
```hzviii.firebaseio.com/.json```
And Bingo we get the Flag:
```{"flag":"HZVIII{f1r3b453_d474b453_m15c0nf16ur4710n}"}```