Tandoor Recipes is an application for managing recipes, planning meals, and building shopping lists. Prior to 2.6.4, RecipeBookViewSet and RecipeBookEntryViewSet use CustomIsShared as an alternative permission class, but CustomIsShared.has_object_permission() returns True for all HTTP methods — including DELETE, PUT, and PATCH — without checking request.method in SAFE_METHODS. Any user who is in the shared list of a RecipeBook can delete or overwrite it, even though shared access is semantically read-only. This vulnerability is fixed in 2.6.4.