We Joined RE:UN10N CTF for Fun and Finished Ninth

“We are going to play for fun only.”

That was what my teammate, Lee Wei Xuan, and I agreed on before registering for RE:UN10N CTF organized by RE:HACK.

We decided to join as a duo to finish our final CTF competition of 2025. Since we only had two people and did not plan to compete too seriously, our initial goal was simply to enjoy the challenges and learn something new.

That plan did not last very long.

Once the competition started, we became increasingly invested in solving the challenges. What was supposed to be a casual session turned into staying up late, discussing clues, testing ideas, and repeatedly checking the scoreboard.

We eventually continued until around 10 or 11 at night on the second day.

Despite entering with a relaxed mindset, we managed to finish in ninth place.

The competition included several interesting categories, but I especially enjoyed the Cyber Threat Intelligence and Kubernetes challenges.

The CTI challenges required us to investigate information, connect small pieces of evidence, and understand the wider context behind an incident. Instead of only analyzing one file, we had to think about relationships between infrastructure, identities, domains, and attacker behaviour.

The Kubernetes challenges were also enjoyable because they involved a different technical environment from the categories I normally focus on. They encouraged me to learn more about containers, orchestration, cluster configurations, and security issues in cloud-native systems.

Competing as a duo created an interesting limitation. With only two people, we could not divide every category among multiple specialists. We had to choose our priorities carefully and constantly communicate what we were investigating.

At the same time, being a small team made collaboration simpler. We always knew what the other person was working on, and we could quickly switch challenges whenever one of us became stuck.

The experience reminded me that CTFs do not always need to begin with a serious competitive goal. Sometimes, joining casually creates less pressure and makes the event more enjoyable.

Of course, once the scoreboard becomes close, the phrase “playing for fun” may quickly disappear.

Thank you to RE:HACK for organizing a fun competition and providing challenges that encouraged us to explore unfamiliar topics.

We joined for fun, lost some sleep, learned about CTI and Kubernetes, and somehow finished ninth. I would consider that a successful final CTF of the year.

RE:UN10N CTF gallery