Is This Stego? Writeup - CubeCTF

Misc/Is This Stego? - rdj & ski

Someone was asking us for a stego challenge, hopefully this is what they were looking for.

Flag format: cube{LAT,LON} with only two digits after the decimal point.

e.g. cube{12.34,-56.78}

Initial Thoughts

We are given a photo of sign that says “STGO”, a fountain, and a flag. Although the challenge hints to it being stego (steganography), the descripton asks for a latitude and longitude. This means it is most likely an OSINT challenge. The sign is the biggest clue, and I figured I could find it pretty easily.

Methodology

I first googled “STGO sign”, yielding some results that looked pretty similar to the sign.

When I added the keyword “fountain” to the search, I didn’t find many helpful results. This was because Google search wanted to autocorrect “stgo” to “santiago”.

I put “stgo” in quotes, which found a helpful result from the Iberia Airlines Travel Guide.

If you scroll through the “How other travellers see it” section, you can find a photo taken in the same place as the original photo. However, the specific location was not given.

At this point, I decided to just use Google images. This found lots of random Instagram photos, and after doing a little profile stalking (this is why your Instagram profile should be private!), I found a photo identifying the location as Cerro San Cristobal, Parque Metropolitano.

Solution

I looked up the coordinates associated with the location, and Google gave (-33.42, -70.63). After trying a few variations, I found one that worked. The flag is cube{-33.41,-70.62}.