HPE NonStop systems support critical environments such as ATMs and transaction processing, yet their security model is often misunderstood, under-assessed, and susceptible to exploitation. In this talk, we will explore the unique NonStop architecture, its approach to security, and all the quirks that make it feel like a mainframe. From there, we will talk about common misconfigurations and design patterns that create unintended exposure. Finally, drawing on real-world assessment experience, we will walk through real-life case studies that demonstrate how seemingly small gaps can escalate into full system control, enabling an attacker to navigate the system with ease to steal some of the most valuable data available.