Cross Session Leak: LLM security vulnerability & detection guide

**Cross-session leak**: the report explains how failures in session isolation and shared caching in multi-user LLM systems can cause sensitive data from one user session (e.g., PHI) to be returned to another user, demonstrated with a healthcare telemedicine assistant case where an attacker obtained patient records through social engineering. It describes detection via dynamic red-teaming probes, preventive controls (per-user isolation, output redaction, access controls, logging, and monitoring), and recommends architectural safeguards and continuous security validation.