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+# Improper Inventory Management (API9:2023)
+Due to the lack of management of API versions, as well as the list of features and case-by-case functions for all functions, it is possible for an attacker to use different functions in different versions of the application.
+
+* Example
+
+GET request to get the list of available API versions:
+
+```html
+GET /api/versions
+```
+
+### Non-compliant code (.NET)
+
+```c#
+[ApiController]
+[Route("api/inventory")]
+public class InventoryController : ControllerBase
+{
+    private readonly IInventoryService _inventoryService;
+    public InventoryController(IInventoryService inventoryService)
+    {
+        _inventoryService = inventoryService;
+    }
+
+    // GET api/inventory/{productId}
+    [HttpGet("{productId}")]
+    public IActionResult GetProductInventory(int productId)
+    {
+        // Fetch inventory data directly from the database
+        var inventory = _inventoryService.GetInventoryByProductId(productId);
+        return Ok(inventory);
+    }
+
+    // POST api/inventory
+    [HttpPost]
+    public IActionResult UpdateProductInventory(InventoryModel inventory)
+    {
+        // Update inventory directly in the database
+        _inventoryService.UpdateInventory(inventory);
+        return Ok();
+    }
+    // Other methods...
+}
+```
+
+
+### Compliant code (.NET)
+```c#
+[ApiController]
+[Route("api/inventory")]
+public class InventoryController : ControllerBase
+{
+    private readonly IInventoryService _inventoryService;
+    public InventoryController(IInventoryService inventoryService)
+    {
+        _inventoryService = inventoryService;
+    }
+
+    // GET api/inventory/{productId}
+    [HttpGet("{productId}")]
+    public IActionResult GetProductInventory(int productId)
+    {
+        // Fetch inventory data through the inventory service
+        var inventory = _inventoryService.GetProductInventory(productId);
+
+        if (inventory == null)
+            return NotFound();
+        return Ok(inventory);
+    }
+
+    // POST api/inventory
+    [HttpPost]
+    [Authorize(Roles = "Admin")] // Restrict access to authorized users with the "Admin" role
+    public IActionResult UpdateProductInventory(InventoryModel inventory)
+    {
+        // Update inventory through the inventory service
+        _inventoryService.UpdateProductInventory(inventory);
+        return Ok();
+    }
+
+    // Other methods...
+}
+```
+
+
+## General prevention suggestions:
+
+* Complete and detailed documentation for the API, including current and previous versions.
+
+* Create a version management system that simplifies updating and managing API versions.
+
+* Introducing a version release policy that includes the time period and support for old versions.
+
+* Using automated methods to check the API version used by customers and warn if old versions are being used.
+
+* Continuous monitoring to detect and fix issues such as outdated API versions and buggy endpoints.
+
+* Use automation methods to automatically check and update API versions and hosts.
+
+* Setting update policies for old API versions and not supporting them.
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