Cross-Application Artifact Namespace Isolation in Google Agent Development Kit (ADK) for Python

Exposure of Resource to Wrong Sphere (CWE-668) in FileArtifactService in Google Agent Development Kit (ADK) for Python (google-adk) versions 1.19.0 before 1.39.1 and 2.0.0a1 before 2.7.0 allows a caller in one application to list, read, overwrite, or delete artifacts belonging to another application when both applications share a FileArtifactService root directory and use the same user_id (and session_id for session-scoped artifacts). FileArtifactService accepted app_name across its public API methods but omitted app_name when constructing on-disk paths (root/users/{user_id}/... instead of root/apps/{app_name}/users/{user_id}/...). Version 2.6.0 scoped writes by app_name but retained a legacy root/users/{user_id} fallback for reads and deletes; version 2.7.0 and the 1.x backport in version 1.39.1 removed the fallback and enforce full per-app path scoping.