When the Scanner Starts Thinking: Learnings from Mythos & GPT 5.5 Cyber in Security Testing

This capability-focused report describes how frontier AI cyber models (Mythos and GPT 5.5 Cyber) enable multi-step reasoning to construct attack paths, generate and validate proof-of-concept exploits, and support vulnerability prioritization, detection engineering, investigations, and remediation; it is an analysis of model capabilities rather than a report of an actual security incident.