Security Researcher · PhD Candidate · CISPA Helmholtz Center for Information Security
Hi, I’m Leon. I’m a security researcher and PhD candidate at CISPA and Saarland University. I study security and privacy problems that emerge at the boundaries between web content, browsers, operating systems, and hardware. My current work also explores secure architectures for AI agents and privacy-preserving bot management.
Advised by Dr. Michael Schwarz and Prof. Christian Rossow.
Selected representative papers.
Modern CSS is expressive enough to reveal information about browsers and email clients without JavaScript. This paper maps that attack surface systematically and evaluates two approaches to mitigating the underlying leakage.
TrueType fonts contain a small instruction language that normally adjusts glyph rendering. This paper shows that those instructions can instead perform cache attacks, enabling website fingerprinting and observation of PDF reading behavior without JavaScript.
WebHID, WebUSB, Web Serial, and Web MIDI give websites direct access to external devices. This paper studies the resulting trust-boundary shift and demonstrates how vulnerable device interfaces can enable firmware replacement and full system compromise.
Security and privacy implications of browser capabilities, from modern CSS features to direct access to external devices.
How information crosses boundaries between web content, browser runtimes, operating systems, and microarchitecture.
System architectures that provide deterministic guarantees, including defenses for AI agents and privacy-preserving bot management.
Full list of publications.
CISPA · TL;DR #44 · podcast
Saarbrücker Zeitung · coverage
Black Hat Asia 2025 · talk
RuhrSec 2025 · talk
Heise Security · coverage
Black Hat MEA 2022 · talk