Cross-user data isolation is the separation that prevents one user’s session, requests, or stored information from being exposed to or affecting another user’s. Applications and services should keep each user’s data and actions within the correct account or session boundary.
In cyber security, a failure of this isolation can let users view or alter other people’s data, or cause one user’s activity to interfere with another’s. In database drivers and tools, flaws in session or connection handling may create such risks. Defenses include securely separating user-specific state, validating authorization on each request, and testing components for cross-account data leakage. The term describes a security property; it does not, by itself, establish that a particular product flaw was exploited.