InventoryGui is a library for creating chest GUIs for Bukkit/Spigot plugins. Versions 1.6.1-SNAPSHOT and earlier contain a vulnerability where any plugin using the `GuiStorageElement can allow item duplication when the experimental Bundle item feature is enabled on the server. The vulnerability is resolved in version 1.6.2-SNAPSHOT.
The product requires that an actor should only be able to perform an action once, or to have only one unique action, but the product does not enforce or improperly enforces this restriction.