Langflow is a tool for building and deploying AI-powered agents and workflows. From 1.0.0 until 1.10.1, Langflow did not verify flow ownership in the deprecated POST /api/v1/build/{flow_id}/vertices and POST /api/v1/build/{flow_id}/vertices/{vertex_id} handlers. Through version 1.7.1, an unauthenticated caller who knew another user's flow UUID could reach these handlers; from version 1.7.2 through 1.10.0, callers had to authenticate but needed no elevated privileges. Such a caller could cause retrieve_vertices_order to load and cache the private graph, enumerate its vertex identifiers, and use build_vertex to execute selected vertices and receive their results. build_graph_from_db_no_cache performed a primary-key lookup without an owner filter. This could disclose private flow structure, configured values, and selected outputs and could trigger victim-configured side effects and build-history records, although it did not expose the victim's variable-store credentials or permit modification of the stored flow. This issue is fixed in Langflow 1.10.1 and langflow-base 0.10.1.