Jaco focused on security hardening for the tschneidereit/wasm-micro-runtime repository, implementing non-executable (NX) stack protection across multiple architectures. He developed architecture-specific assembly markers to ensure stacks are marked non-executable, directly addressing the risk of stack-based exploits. By standardizing NX markers, Jaco improved cross-architecture consistency, which simplifies future code audits and security reviews. His work maintained runtime performance by applying optimizations tailored to each architecture. Using Assembly Language and leveraging expertise in low-level programming and system security, Jaco delivered a targeted feature that enhances the security posture of the runtime without introducing regressions or requiring major changes to existing code.