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CTF WriteupOSINT

DIVER OSINT CTF 2026 Writeup

Writeup for challenges solved during DIVER OSINT CTF 2026. My first CTF experience, focusing on OSINT techniques and tools.

3 min read
Competition Overview
  • Team: Bao Bao
  • User: yuerei
  • Final Standing: 239th place
  • Focus Areas: OSINT

Introduction#

read_qr (100pt / 547 solves)#

What URL is stored in this QR code? If it is https://x.com/DIVER_OSINT_CTF, the flag should be Diver26{https://x.com/DIVER_OSINT_CTF}.

read_qr Challenge Image

Once I downloaded the image I immediately scanned it with my phone, which revealed the URL https://qr.intro26.workers.dev/q/y0u_r34d_7h3_qr_wi7h0u7_4cc3ss. The flag was then formatted as:

DIVER26{https://qr.intro26.workers.dev/q/y0u_r34d_7h3_qr_wi7h0u7_4cc3ss}.

momo (100pt / 558 solves)#

I took a photo of an aircraft in April 2026, but I forgot to photograph its registration number. Find out and answer the registration number of the aircraft shown in the photo. If the registration number is JA380A, the flag should be Diver26{JA380A}.

momo Challenge Image

I found this website to see the special livery of the aircraft:

Peach Fleet Details and History

www.planespotters.net

Special Colors / Stickers, and I saw one with the same design as the challenge image, with Remark lsd, "Taihei Dengyo" sticker. It's JA823P

Diver26{JA823P}

owner (100pt / 590 solves)#

Answer the country which owns this vehicle in English. For example, if it is Japan, the flag should be Diver26{Japan}.

owner Challenge Image

A diplomat number 外 (gaikoku, meaning foreign). Googling it will come out with Australia.

Diver26{Australia}

8pm (100pt / 387 solves)#

What was the first specific facility featured in the news program broadcast on Korean Central Television at 8:00 PM (local time) on July 2, 2026? Answer using the OpenStreetMap Way ID. However, provide the Way ID representing the entire site, not an individual building. For example, if the way number is 1234567890, the flag should be Diver26{1234567890}.

Searched for KCNA Watch and found the broadcast on July 2, 2026, at 8:00 PM.

8pm Challenge Image

The building in the image is the Pyonyang Elementary School, which has the OpenStreetMap Way ID 1131937005.

Pyongyang Elementary School - Google Maps

www.google.com

Way: 1131937005

OpenStreetMap is a map of the world, created by people like you and free to use under an open license.

www.openstreetmap.org

Diver26{1131937005}

misc#

nui (100pt / 242 solves)#

nui Challenge Image

Searched for the image using Google Lens and found a Nasa webpage for the original image. Downloaded it and checked the metadata using https://exif.tools/ and found the following information:

Make	                samsung
Model	                Galaxy S23 Ultra
Create Date             2026-01-28T07:48:28.000Z
Date Time Digitized     2026:01:28 14:48:28
Date Time Original  	2026-01-28T07:48:28.000Z | 2026:01:28 14:48:28

Diver26{20260128_Galaxy S23 Ultra}

Conclusion#

This competition was a great for my first CTF and OSINT experience. I learned a lot about different techniques and tools. Looking forward to participating in more CTFs in the future and improving my skills further.

Did not know Swimmer exist... maybe next time I will participate in Swimmer CTF.