GCombo

Category: Misc
Points: 36

Challenge

One day I spied out my friend accessing some google form to enter his secret combination lock. Afterwards, I kept bothering him about it, and he finally decided to give the link to me. Maybe you can figure out his combo for me and get a tasty flag in return:

link

By: theKidOfArcrania

Solution

Made a test google form:

So the section numbers are significant. Where do we find them on the page?

What happens when we submit the form?

So entry.203483032 holds the option we selected (8 in this case).

Let's try to explore all pages by sending requests like this. Finally we get here:

Searching the HTML, we see this weird JSON thingy called FB_PUBLIC_LOAD_DATA_. Turns out we could've used it to solve the challenge offline, but oh well.

We find this:

[766405565,"Password Please",null,0,[[1674649702,null,1,null,[[4,301,["s3cuR3_p1n_id_2_3v3ry0ne"]

Finally we get to the end:

Script output:

Doing page 0:
11 11 11 11 11 12 11 11 11 11
Doing page 11:
 4  4  4  4  4 11  4  4  4  4
Doing page 12:
 4  4  4  4  4  4  4  4  5  4
...
Doing page 17:
20 11 11 13 11  6 15  4  1 18
Doing page 13:
 7 20 20 20 20  9  9 19  1  7
Doing page 19:
Pin: [5, 8, 1, 2, 6, 9, 3, 3, 7, 0]
Flag: pbctf{5812693370_s3cuR3_p1n_id_2_3v3ry0ne}

What a cool challenge 😄