# WooCommerce REST API allows duplicate SKUs when SKU is passed via meta_data
## The problem
I create products through the WooCommerce REST API (`POST /wp-json/wc/v3/products`) and pass the SKU inside `meta_data` as `{"key": "_sku", "value": "1234567890"}`. I was able to create multiple products with the same SKU. Shouldn't the duplicate SKU be rejected?
## The verified fix
This was a real bug: when you send `_sku` inside `meta_data`, it bypassed `WC_Product::set_sku()` and went through `MetaDataUtil::update()` instead, so the SKU uniqueness check (`wc_product_has_unique_sku()`) never ran. It was fixed by PR #31168. On a current WooCommerce version, the same request now returns a `400 product_invalid_sku` error on the second product with the same SKU, and only one product persists. The recommended practice anyway: send `sku` as the top-level field, not inside `meta_data`, since top-level always goes through the proper setter.
Source: https://github.com/woocommerce/woocommerce/issues/29286