An app-in-app is an embedded application that runs inside another platform, such as a chat assistant, messaging app, or marketplace. Instead of sending the user to a separate website, the host platform renders a smaller workflow for browsing, booking, ordering, or payment inside its own interface.
In cyber security, this matters because the host controls the container, the permissions, and often the data path. That creates a larger attack surface: malicious embedded content, weak API controls, or injected instructions can influence rankings, forms, or state-changing actions. Defenders should treat the embedded app as untrusted until verified, use least-privilege permissions, validate every structured request, sandbox external content, and require explicit confirmation for purchases or other sensitive actions.