Niklas Gögge works on finding, fixing and responsibly disclosing bugs in Bitcoin, and on building out Bitcoin Core's testing infrastructure. Brink funds him full time, with a stated focus on making the peer-to-peer code more robust through review, testing and fuzzing.
The peer-to-peer layer is where a node meets strangers. Everything arriving on it is attacker-controlled input, so the useful question is not whether the code handles correct messages but what it does with malformed ones, and fuzzing is the systematic way to ask that a few million times.
He is one of three people whose PGP keys are published in the Bitcoin Core repository for reporting security vulnerabilities, alongside Michael Ford and Ava Chow. He also serves on Brink's grant committee with Mike Schmidt and Cory Fields, which means he helps decide who else gets funded.