Tandoor Recipes is an application for managing recipes, planning meals, and building shopping lists. Prior to 2.6.12, StepViewSet and IngredientViewSet filter only by active Space and use role-level CustomIsUser checks instead of the private-recipe owner or sharing predicate when an authenticated user with read and write API scope in the victim's Space supplies a private recipe or step identifier to the Step API. Request processing uses StepViewSet, IngredientViewSet, api/step/, api/step/{step_id}/, CustomIsUser, CustomRecipePermission. The attack works because the sub-resource querysets return and update private-recipe steps for non-owners because Space membership is accepted without recipe-level authorization. This can read and silently modify another same-Space member's private recipe instructions, while cross-Space access remains out of scope. This issue is fixed in version 2.6.12.