diff --git a/plugins/woocommerce/changelog/fix-25623 b/plugins/woocommerce/changelog/fix-25623
new file mode 100644
index 00000000000..d62ea1afc9d
--- /dev/null
+++ b/plugins/woocommerce/changelog/fix-25623
@@ -0,0 +1,4 @@
+Significance: patch
+Type: fix
+
+Prevent reading items with zero order ID to avoid mixups.
diff --git a/plugins/woocommerce/includes/data-stores/abstract-wc-order-data-store-cpt.php b/plugins/woocommerce/includes/data-stores/abstract-wc-order-data-store-cpt.php
index 05a4efbadba..5cf6c4344e5 100644
--- a/plugins/woocommerce/includes/data-stores/abstract-wc-order-data-store-cpt.php
+++ b/plugins/woocommerce/includes/data-stores/abstract-wc-order-data-store-cpt.php
@@ -12,6 +12,7 @@ if ( ! defined( 'ABSPATH' ) ) {
 	exit;
 }
 
+// phpcs:disable Squiz.Classes.ClassFileName.NoMatch, Squiz.Classes.ValidClassName.NotCamelCaps -- Backward compatibility.
 /**
  * Abstract Order Data Store: Stored in CPT.
  *
@@ -80,6 +81,13 @@ abstract class Abstract_WC_Order_Data_Store_CPT extends WC_Data_Store_WP impleme
 		}
 
 		$id = wp_insert_post(
+			/**
+			 * Filters the data for a new order before it is inserted into the database.
+			 *
+			 * @param array $data Array of data for the new order.
+			 *
+			 * @since 3.3.0
+			 */
 			apply_filters(
 				'woocommerce_new_order_data',
 				array(
@@ -115,7 +123,7 @@ abstract class Abstract_WC_Order_Data_Store_CPT extends WC_Data_Store_WP impleme
 	 * @param int $order_id The order id to check.
 	 * @return bool True if an order exists with the given name.
 	 */
-	public function order_exists( $order_id ) : bool {
+	public function order_exists( $order_id ): bool {
 		if ( ! $order_id ) {
 			return false;
 		}
@@ -135,7 +143,7 @@ abstract class Abstract_WC_Order_Data_Store_CPT extends WC_Data_Store_WP impleme
 		$order->set_defaults();
 		$post_object = get_post( $order->get_id() );
 		if ( ! $order->get_id() || ! $post_object || ! in_array( $post_object->post_type, wc_get_order_types(), true ) ) {
-			throw new Exception( __( 'Invalid order.', 'woocommerce' ) );
+			throw new Exception( esc_html__( 'Invalid order.', 'woocommerce' ) );
 		}
 
 		$this->set_order_props(
@@ -291,7 +299,7 @@ abstract class Abstract_WC_Order_Data_Store_CPT extends WC_Data_Store_WP impleme
 				/**
 				 * Fires immediately after an order is deleted.
 				 *
-				 * @since
+				 * @since 2.7.0
 				 *
 				 * @param int $order_id ID of the order that has been deleted.
 				 */
@@ -345,6 +353,13 @@ abstract class Abstract_WC_Order_Data_Store_CPT extends WC_Data_Store_WP impleme
 		$order_status = $order->get_status( 'edit' );
 
 		if ( ! $order_status ) {
+			/**
+			 * Filters the default order status to use when creating a new order.
+			 *
+			 * @param string $order_status Default order status.
+			 *
+			 * @since 3.7.0
+			 */
 			$order_status = apply_filters( 'woocommerce_default_order_status', 'pending' );
 		}
 
@@ -352,7 +367,7 @@ abstract class Abstract_WC_Order_Data_Store_CPT extends WC_Data_Store_WP impleme
 		$valid_statuses = get_post_stati();
 
 		// Add a wc- prefix to the status, but exclude some core statuses which should not be prefixed.
-		// @todo In the future this should only happen based on `wc_is_order_status`, but in order to
+		// In the future this should only happen based on `wc_is_order_status`, but in order to
 		// preserve back-compatibility this happens to all statuses except a select few. A doing_it_wrong
 		// Notice will be needed here, followed by future removal.
 		if ( ! in_array( $post_status, array( 'auto-draft', 'draft', 'trash' ), true ) && in_array( 'wc-' . $post_status, $valid_statuses, true ) ) {
@@ -380,7 +395,7 @@ abstract class Abstract_WC_Order_Data_Store_CPT extends WC_Data_Store_WP impleme
 	protected function get_post_title() {
 		// @codingStandardsIgnoreStart
 		/* translators: %s: Order date */
-		return sprintf( __( 'Order – %s', 'woocommerce' ), (new DateTime('now'))->format( _x( 'M d, Y @ h:i A', 'Order date parsed by DateTime::format', 'woocommerce' ) ) );
+		return sprintf( __( 'Order – %s', 'woocommerce' ), ( new DateTime( 'now' ) )->format( _x( 'M d, Y @ h:i A', 'Order date parsed by DateTime::format', 'woocommerce' ) ) );
 		// @codingStandardsIgnoreEnd
 	}
 
@@ -466,6 +481,14 @@ abstract class Abstract_WC_Order_Data_Store_CPT extends WC_Data_Store_WP impleme
 			}
 		}
 
+		/**
+		 * Action fired after updating order properties.
+		 *
+		 * @param WC_Abstract_Order $order Order object.
+		 * @param string[]          $updated_props Array of updated properties.
+		 *
+		 * @since 2.7.0
+		 */
 		do_action( 'woocommerce_order_object_updated_props', $order, $updated_props );
 	}
 
@@ -491,6 +514,11 @@ abstract class Abstract_WC_Order_Data_Store_CPT extends WC_Data_Store_WP impleme
 	public function read_items( $order, $type ) {
 		global $wpdb;
 
+		// When the order is not yet saved, we cannot get the items from DB. Trying to do so will risk reading items of different orders that were saved incorrectly.
+		if ( 0 === $order->get_id() ) {
+			return array();
+		}
+
 		// Get from cache if available.
 		$items = 0 < $order->get_id() ? wp_cache_get( 'order-items-' . $order->get_id(), 'orders' ) : false;
 
diff --git a/plugins/woocommerce/tests/php/includes/abstracts/class-wc-abstract-order-test.php b/plugins/woocommerce/tests/php/includes/abstracts/class-wc-abstract-order-test.php
index 82adf8dac62..04ea2d0c950 100644
--- a/plugins/woocommerce/tests/php/includes/abstracts/class-wc-abstract-order-test.php
+++ b/plugins/woocommerce/tests/php/includes/abstracts/class-wc-abstract-order-test.php
@@ -7,6 +7,7 @@
 
 use Automattic\WooCommerce\Testing\Tools\CodeHacking\Hacks\FunctionsMockerHack;
 
+// phpcs:disable Squiz.Classes.ClassFileName.NoMatch, Squiz.Classes.ValidClassName.NotCamelCaps -- Backward compatibility.
 /**
  * Class WC_Abstract_Order.
  */
@@ -148,7 +149,7 @@ class WC_Abstract_Order_Test extends WC_Unit_Test_Case {
 
 		FunctionsMockerHack::add_function_mocks(
 			array(
-				'wc_get_price_excluding_tax' => function( $product, $args = array() ) use ( &$product_passed_to_get_price, &$args_passed_to_get_price ) {
+				'wc_get_price_excluding_tax' => function ( $product, $args = array() ) use ( &$product_passed_to_get_price, &$args_passed_to_get_price ) {
 						$product_passed_to_get_price = $product;
 						$args_passed_to_get_price    = $args;
 
@@ -311,7 +312,7 @@ class WC_Abstract_Order_Test extends WC_Unit_Test_Case {
 	public function test_cache_does_not_interferes_with_order_object() {
 		add_action(
 			'woocommerce_new_order',
-			function( $order_id ) {
+			function ( $order_id ) {
 				// this makes the cache store a specific order class instance, but it's quickly replaced by a generic one
 				// as we're in the middle of a save and this gets executed before the logic in WC_Abstract_Order.
 				$order = wc_get_order( $order_id );
@@ -348,4 +349,45 @@ class WC_Abstract_Order_Test extends WC_Unit_Test_Case {
 		$order_terms = wp_list_pluck( wp_get_object_terms( $order->get_id(), $custom_taxonomy->name ), 'name' );
 		$this->assertContains( 'new_term', $order_terms );
 	}
+
+	/**
+	 * @testDox Test that order items are not mixed when order_id is zero.
+	 */
+	public function test_order_items_shouldnot_mix_with_zero_id() {
+		$order1 = new WC_Order();
+		$order2 = new WC_Order();
+
+		$product1_for_order1 = WC_Helper_Product::create_simple_product();
+		$product2_for_order1 = WC_Helper_Product::create_simple_product();
+		$product_for_order2  = WC_Helper_Product::create_simple_product();
+
+		$item1_1 = new WC_Order_Item_Product();
+		$item1_1->set_product( $product1_for_order1 );
+		$item1_1->set_quantity( 1 );
+		$item1_1->save();
+
+		$item1_2 = new WC_Order_Item_Product();
+		$item1_2->set_product( $product2_for_order1 );
+		$item1_2->set_quantity( 1 );
+		$item1_2->save();
+
+		$item2 = new WC_Order_Item_Product();
+		$item2->set_product( $product_for_order2 );
+		$item2->set_quantity( 1 );
+		$item2->save();
+
+		$order1->add_item( $item1_1 );
+		$order2->add_item( $item2 );
+		$order1->add_item( $item1_2 );
+
+		$this->assertCount( 1, $order2->get_items( 'line_item' ) );
+		$this->assertCount( 2, $order1->get_items( 'line_item' ) );
+
+		$order1_items = array_keys( $order1->get_items( 'line_item' ) );
+
+		$this->assertContains( $item1_1->get_id(), $order1_items );
+		$this->assertContains( $item1_1->get_id(), $order1_items );
+
+		$this->assertEquals( $item2->get_id(), array_keys( $order2->get_items( 'line_item' ) )[0] );
+	}
 }