Hej Hej Stockholm: Valentine’s Edition of the CISPA European Cybersecurity & AI Hackathon Championship in Sweden

Icy air, bright blue skies, and the scent of cinnamon buns: it sounds like the perfect Valentine’s weekend in Stockholm. Yet not far from the narrow streets of the old town, where couples spent the day romantically, students bent over their laptops, puzzling over complex tasks, their tables crowded with coffee cups and pizza boxes. Nearly 60 early-career researchers in AI and cybersecurity had gathered here for the hackathon championship.

Visual impressions from the first day

At the welcome session on Saturday afternoon in the lecture hall, the excitement among the students—who had traveled from around the world—was clearly palpable. No one yet knew exactly how the weekend would unfold or which challenges awaited the teams. One question hung over the participants: Am I up to the task?

The project’s initiators, CISPA faculty members Adam Dziedzic and Franziska Boenisch, quickly created an open atmosphere. At the Stockholm edition, they were also supported by CISPA faculty member Thorsten Eisenhofer. Before long, students were deep in conversation, and a focused working atmosphere emerged. Alongside presenting the challenges, the three faculty members also provided a brief thematic introduction. “The tasks are completely different each time,” Boenisch explained during a break. “We want to ensure no one has an advantage while covering as broad a spectrum of topics in AI and cybersecurity as possible. It’s great that our colleague Thorsten is contributing a challenge this time as well.”

Tasks from everyday research for the hackathon

The competition featured three tasks covering private data and model training, ML model misclassification, and model attribution. Boenisch explained the first example: “When training LLMs, sensitive or private information can unintentionally enter the training data. The task aims to exploit so-called model inversion. Participants were given access to the model and asked to reconstruct the original training data. The best solution is the one where the reconstructed datasets most closely match the original training data.” This challenge highlights a central issue in modern AI systems: even when training data are not directly accessible, models can under certain conditions reveal information about their training content—a risk intensively studied at CISPA.

Visual impressions from the second day

International CISPA staff members, including colleagues from the Scientific Talent Acquisition Team, also used the event to connect with participants from around the world. During breaks, the international atmosphere was especially noticeable, with conversations in many different languages heard in nearly every corner.
For CISPA, the hackathon championship offers an excellent opportunity to engage with young researchers in an informal setting—discussing master’s thesis supervision, internships at CISPA, and general career paths in AI and cybersecurity research.

The lucky winning teams from Stockholm

In the end, three teams (SeeWeedZ, Polarnutt and The White House) impressed the jury in Stockholm. Participants were at very different stages of their careers: while some were still in their bachelor’s programs, others had already worked in the IT sector for several years. Despite these differences, they will compete in July 2026 at CISPA against the winners of the other regional qualifiers. Until then, there is still time to prepare—and to study research papers intensively, since many challenges are based on academic publications, including numerous papers authored by CISPA researchers.

After the award ceremony on Sunday afternoon, as the adrenaline slowly faded, the rooms at KTH gradually emptied. Tension gave way to visible exhaustion—both among the participating teams, many of whom had worked through the night with only short breaks, and among the organizing team.

Behind the scenes, too, the event required full commitment. Julian Collet, who coordinated organizational efforts for CISPA, drew a positive conclusion:
“By our third hackathon, we have become a well-coordinated team across administration and research,” he said. “We’re looking forward to the upcoming events, new challenges—and to meeting many more young talents in cybersecurity research.”

The next regional qualifier will take place on March 21–22, 2026, in Munich.

Our Team in Stockholm

About the Hackathon Championship

The CISPA European Cybersecurity & AI Hackathon Championship is a Europe-wide competition running from November 2025 to June 2026, organized by the CISPA Helmholtz Center for Information Security. Across regional rounds in major European university cities, Bachelor’s and Master’s students will form teams of up to four to tackle AI-and cybersecurity-focused challenges over 24 hours. Winners from each region will advance to the Grand Finale in St. Ingbert, Germany competing for cash prizes, trophies, and certificates. By bringing together young talent from across the continent, this Championship aims not only to foster innovation and skills in trustworthy AI and cybersecurity but also to build a pan-European community invested in securing our digital future.