EchoLeak: Anatomy of a Zero-Click Prompt Injection and How to Prevent the Next One

Pavan Reddy April 17, 2026 EchoLeak (CVE-2025-32711) is a concrete example of “prompt injection becomes a breach”: a reported vulnerability affecting Microsoft 365 Copilot associated with unauthorized information disclosure over a network. This talk dissects the engineering failure as a repeatable learning model: where trust boundaries were crossed, why layered mitigations didn’t fully hold, and how real systems accidentally grant models the ability to move data across compartments. Attendees will leave with a defensive blueprint that applies beyond this incident, design patterns for provenance isolation, retrieval compartmentalization, least-privilege tool design, output controls, and a test plan for continuous adversarial evaluation that can be integrated into shipping pipelines.