DIVER OSINT CTF is a real-world OSINT CTF with challenges in English and Japanese. The 2026 edition ran for 24 hours from 25 to 26 July. These are my writeups for four of its challenges, each with the queries and the dead ends, not just the flag.
| Challenge | What it takes | Difficulty |
|---|---|---|
| From a Blurry Container Photo to an IMO Number | Reading a container number off a low-resolution harbour photo, then following the shipping chain to the vessel | medium |
| Nine Kilometres Off: Geolocating an Airstrike Photo in Mogok Township | Geolocation when the caption’s place name is administrative, not geographic | hard |
| A Concert Seat from a LinkedIn Lead | A cross-platform pivot from a profile to a travel vlog, and one blurry ticket frame | medium |
| REACH 4599 — Why the Yellow Sea C-17 Was Not a Secret Flight | Checking a flight-tracking claim against the leg history in the same screenshot | easy |
The organisers publish their own solutions in the official writeup archive on GitHub. Read theirs for the intended path, and these for how the path looked from the outside, including where it went wrong.