diff --git a/platforms/react-native/README.md b/platforms/react-native/README.md
index 4c91fba96..13efdaeb5 100644
--- a/platforms/react-native/README.md
+++ b/platforms/react-native/README.md
@@ -347,6 +347,7 @@ instance of the `ShopifyCheckout` class.
 | `preloading`  |          | `true`      | Enable/disable [preloading](#preloading).                                                                                                                      |
 | `colors`      |          | `{}`        | An object with `ios` and `android` properties to override the colors for iOS and Android platforms individually. See [`colors`](#colors) for more information. |
 | `logLevel`    |          | `error`     | Sets the log level for the native SDK. Use `LogLevel.debug` for verbose logging during development, or `LogLevel.error` for production.                        |
+| `allowedMessageOrigins` |          | `[]`        | Extra origins trusted to send incoming checkout messages. See [Incoming message origin validation](#incoming-message-origin-validation).                       |
 
 Here's an example of how a fully customized configuration object might look:
 
@@ -468,6 +469,29 @@ function AppWithContext() {
 }
 ```
 
+### Incoming message origin validation
+
+Native checkout accepts messages from every origin by default. To restrict
+messages, configure one or more exact origins or wildcard subdomains. The
+checkout URL's origin and `shop.app` remain trusted automatically.
+
+```tsx
+const config: Configuration = {
+  allowedMessageOrigins: [
+    'https://checkout.example.com',
+    'https://*.example.org',
+  ],
+};
+```
+
+Entries may be exact origins (`https://example.com`), wildcard subdomains
+(`https://*.example.com`, matching subdomains but not the apex), or `'*'` to
+explicitly disable origin validation.
+
+Messages dropped by origin validation are never silently discarded: the native
+SDK logs each rejection as a warning with the message origin and the reason it
+was dropped. The message body is untrusted and is not logged.
+
 ### Localization
 
 #### Checkout Sheet title
diff --git a/platforms/react-native/modules/@shopify/checkout-kit-react-native/android/src/main/java/com/shopify/reactnative/checkoutkit/ShopifyCheckoutKitModule.java b/platforms/react-native/modules/@shopify/checkout-kit-react-native/android/src/main/java/com/shopify/reactnative/checkoutkit/ShopifyCheckoutKitModule.java
index 40a3354b5..2762a65ac 100644
--- a/platforms/react-native/modules/@shopify/checkout-kit-react-native/android/src/main/java/com/shopify/reactnative/checkoutkit/ShopifyCheckoutKitModule.java
+++ b/platforms/react-native/modules/@shopify/checkout-kit-react-native/android/src/main/java/com/shopify/reactnative/checkoutkit/ShopifyCheckoutKitModule.java
@@ -13,10 +13,12 @@
 
 import java.util.ArrayList;
 import java.util.HashMap;
+import java.util.HashSet;
 import java.util.List;
 import java.util.Locale;
 import java.util.Map;
 import java.util.Objects;
+import java.util.Set;
 
 public class ShopifyCheckoutKitModule extends NativeShopifyCheckoutKitSpec {
 
@@ -125,6 +127,8 @@ public WritableMap getConfig() {
     resultConfig.putString("colorScheme", colorSchemeStringFor(checkoutConfig.getAppearance()));
     resultConfig.putString("logLevel", logLevelStringFor(checkoutConfig.getLogLevel()));
     resultConfig.putBoolean("preloading", checkoutConfig.getPreloading().getEnabled());
+    resultConfig.putArray("allowedMessageOrigins",
+        Arguments.fromList(new ArrayList<>(checkoutConfig.getAllowedMessageOrigins())));
 
     return resultConfig;
   }
@@ -140,6 +144,10 @@ public void setConfig(ReadableMap config) {
         configuration.setPreloading(new Preloading(config.getBoolean("preloading")));
       }
 
+      if (config.hasKey("allowedMessageOrigins")) {
+        configuration.setAllowedMessageOrigins(toStringSet(config.getArray("allowedMessageOrigins")));
+      }
+
       if (config.hasKey("logLevel")) {
         LogLevel logLevel = logLevelFor(config.getString("logLevel"));
 
@@ -168,6 +176,20 @@ public void setConfig(ReadableMap config) {
     });
   }
 
+  private static Set<String> toStringSet(ReadableArray array) {
+    Set<String> values = new HashSet<>();
+    if (array == null) {
+      return values;
+    }
+    for (int i = 0; i < array.size(); i++) {
+      String value = array.getString(i);
+      if (value != null) {
+        values.add(value);
+      }
+    }
+    return values;
+  }
+
   @ReactMethod(isBlockingSynchronousMethod = true)
   public boolean configureAcceleratedCheckouts(
       String storefrontDomain,
diff --git a/platforms/react-native/modules/@shopify/checkout-kit-react-native/ios/ShopifyCheckoutKit.swift b/platforms/react-native/modules/@shopify/checkout-kit-react-native/ios/ShopifyCheckoutKit.swift
index 1a35c076d..00e0869f5 100644
--- a/platforms/react-native/modules/@shopify/checkout-kit-react-native/ios/ShopifyCheckoutKit.swift
+++ b/platforms/react-native/modules/@shopify/checkout-kit-react-native/ios/ShopifyCheckoutKit.swift
@@ -164,6 +164,10 @@ class RCTShopifyCheckoutKit: NSObject {
             ShopifyCheckoutKit.configuration.preloading.enabled = preloading
         }
 
+        if let allowedMessageOrigins = configuration["allowedMessageOrigins"] as? [String] {
+            ShopifyCheckoutKit.configuration.allowedMessageOrigins = allowedMessageOrigins
+        }
+
         if let colorScheme = configuration["colorScheme"] as? String,
            let appearance = appearanceFor(colorScheme)
         {
@@ -199,6 +203,7 @@ class RCTShopifyCheckoutKit: NSObject {
             "tintColor": ShopifyCheckoutKit.configuration.tintColor,
             "backgroundColor": ShopifyCheckoutKit.configuration.backgroundColor,
             "closeButtonColor": ShopifyCheckoutKit.configuration.closeButtonTintColor,
+            "allowedMessageOrigins": ShopifyCheckoutKit.configuration.allowedMessageOrigins,
             "logLevel": logLevelToString(ShopifyCheckoutKit.configuration.logLevel)
         ]
     }
diff --git a/platforms/react-native/modules/@shopify/checkout-kit-react-native/package.json b/platforms/react-native/modules/@shopify/checkout-kit-react-native/package.json
index b1900248d..f02701faf 100644
--- a/platforms/react-native/modules/@shopify/checkout-kit-react-native/package.json
+++ b/platforms/react-native/modules/@shopify/checkout-kit-react-native/package.json
@@ -19,8 +19,8 @@
   },
   "checkoutKit": {
     "nativeSdkVersions": {
-      "ios": "4.0.0-alpha.4",
-      "android": "4.0.0-alpha.4"
+      "ios": "4.0.0-alpha.5",
+      "android": "4.0.0-alpha.5"
     }
   },
   "scripts": {
diff --git a/platforms/react-native/modules/@shopify/checkout-kit-react-native/src/index.d.ts b/platforms/react-native/modules/@shopify/checkout-kit-react-native/src/index.d.ts
index e274b9993..de437dcbb 100644
--- a/platforms/react-native/modules/@shopify/checkout-kit-react-native/src/index.d.ts
+++ b/platforms/react-native/modules/@shopify/checkout-kit-react-native/src/index.d.ts
@@ -113,6 +113,22 @@ interface CommonConfiguration {
    * @default true
    */
   preloading?: boolean;
+  /**
+   * Origins trusted to send incoming checkout messages, in addition to the
+   * loaded checkout origin and `shop.app` (including its subdomains).
+   *
+   * The native surface is open by default: when this is empty (the default),
+   * messages from any origin are accepted. Provide one or more origins to
+   * restrict which origins are trusted. Entries may be exact origins
+   * (`https://example.com`), wildcard subdomains (`https://*.example.com`), or
+   * `'*'` to explicitly disable origin validation.
+   *
+   * Rejected messages are never silently dropped: the native SDK logs each
+   * rejection as a warning with the message origin and reason.
+   *
+   * @default [] (all origins trusted)
+   */
+  allowedMessageOrigins?: string[];
 }
 
 export type Configuration = CommonConfiguration & {
diff --git a/platforms/react-native/modules/@shopify/checkout-kit-react-native/src/specs/NativeShopifyCheckoutKit.ts b/platforms/react-native/modules/@shopify/checkout-kit-react-native/src/specs/NativeShopifyCheckoutKit.ts
index c4bcaee5e..d1eed9157 100644
--- a/platforms/react-native/modules/@shopify/checkout-kit-react-native/src/specs/NativeShopifyCheckoutKit.ts
+++ b/platforms/react-native/modules/@shopify/checkout-kit-react-native/src/specs/NativeShopifyCheckoutKit.ts
@@ -35,6 +35,7 @@ type ConfigurationSpec = {
   colorScheme?: string;
   logLevel?: string;
   preloading?: boolean;
+  allowedMessageOrigins?: string[];
   colors?: ColorsSpec;
 };
 
@@ -46,6 +47,7 @@ type ConfigurationResultSpec = {
   tintColor?: string;
   backgroundColor?: string;
   closeButtonColor?: string;
+  allowedMessageOrigins: string[];
 };
 
 export interface Spec extends TurboModule {
diff --git a/platforms/react-native/modules/@shopify/checkout-kit-react-native/tests/index.test.ts b/platforms/react-native/modules/@shopify/checkout-kit-react-native/tests/index.test.ts
index fc949e42a..c254468b0 100644
--- a/platforms/react-native/modules/@shopify/checkout-kit-react-native/tests/index.test.ts
+++ b/platforms/react-native/modules/@shopify/checkout-kit-react-native/tests/index.test.ts
@@ -209,6 +209,18 @@ describe('ShopifyCheckoutKit', () => {
       instance.setConfig(configWithTitle);
       expect(NativeModule.setConfig).toHaveBeenCalledWith(configWithTitle);
     });
+
+    it('calls `setConfig` with allowedMessageOrigins configuration', () => {
+      const instance = new ShopifyCheckout();
+      const configWithAllowedOrigins: Configuration = {
+        colorScheme: ColorScheme.automatic,
+        allowedMessageOrigins: ['https://example.com', 'https://*.example.com'],
+      };
+      instance.setConfig(configWithAllowedOrigins);
+      expect(NativeModule.setConfig).toHaveBeenCalledWith(
+        configWithAllowedOrigins,
+      );
+    });
   });
 
   describe('preload', () => {
@@ -668,6 +680,24 @@ describe('ShopifyCheckoutKit', () => {
       expect(result.logLevel).toBe('trace');
       expect(result.colorScheme).toBe('sepia');
     });
+
+    it('returns configured allowed message origins', () => {
+      NativeModule.getConfig.mockReturnValueOnce({
+        colorScheme: 'automatic',
+        logLevel: 'error',
+        preloading: true,
+        allowedMessageOrigins: ['https://example.com'],
+      });
+
+      const instance = new ShopifyCheckout();
+
+      expect(instance.getConfig()).toStrictEqual({
+        colorScheme: ColorScheme.automatic,
+        logLevel: LogLevel.error,
+        preloading: true,
+        allowedMessageOrigins: ['https://example.com'],
+      });
+    });
   });
 
   describe('Geolocation', () => {
diff --git a/platforms/react-native/sample/android/app/src/test/java/com/shopify/checkoutkit/reactnativedemo/ShopifyCheckoutKitModuleTest.java b/platforms/react-native/sample/android/app/src/test/java/com/shopify/checkoutkit/reactnativedemo/ShopifyCheckoutKitModuleTest.java
index 1a66e8940..3fbbde26e 100644
--- a/platforms/react-native/sample/android/app/src/test/java/com/shopify/checkoutkit/reactnativedemo/ShopifyCheckoutKitModuleTest.java
+++ b/platforms/react-native/sample/android/app/src/test/java/com/shopify/checkoutkit/reactnativedemo/ShopifyCheckoutKitModuleTest.java
@@ -78,6 +78,8 @@ public void setup() {
     mocks = MockitoAnnotations.openMocks(this);
     mockedArguments = Mockito.mockStatic(Arguments.class);
     mockedArguments.when(Arguments::createMap).thenAnswer(invocation -> new JavaOnlyMap());
+    mockedArguments.when(() -> Arguments.fromList(anyList()))
+        .thenAnswer(invocation -> JavaOnlyArray.from(invocation.getArgument(0)));
 
     when(mockReactContext.getCurrentActivity()).thenReturn(mockComponentActivity);
     shopifyCheckoutKitModule = new ShopifyCheckoutKitModule(mockReactContext);
@@ -317,6 +319,22 @@ public void testUnknownColorSchemeKeepsTheNativeDefaultAppearance() {
         .isEqualTo("storefront");
   }
 
+  @Test
+  public void testAllowedMessageOriginsRoundTrip() {
+    JavaOnlyMap config = new JavaOnlyMap();
+    JavaOnlyArray allowedMessageOrigins = new JavaOnlyArray();
+    allowedMessageOrigins.pushString("https://example.com");
+    allowedMessageOrigins.pushString("https://*.example.com");
+    config.putArray("allowedMessageOrigins", allowedMessageOrigins);
+
+    shopifyCheckoutKitModule.setConfig(config);
+
+    assertThat(ShopifyCheckoutKitModule.checkoutConfig.getAllowedMessageOrigins())
+        .containsExactlyInAnyOrder("https://example.com", "https://*.example.com");
+    assertThat(shopifyCheckoutKitModule.getConfig().getArray("allowedMessageOrigins").toArrayList())
+        .containsExactlyInAnyOrder("https://example.com", "https://*.example.com");
+  }
+
   @Test
   public void testCanConfigureLightColorSchemeWithValidColors() {
     JavaOnlyMap androidColors = createValidLightColors();
diff --git a/platforms/react-native/sample/ios/Podfile.lock b/platforms/react-native/sample/ios/Podfile.lock
index 09a6a9807..a2b196f5f 100644
--- a/platforms/react-native/sample/ios/Podfile.lock
+++ b/platforms/react-native/sample/ios/Podfile.lock
@@ -2605,8 +2605,8 @@ PODS:
     - ReactCodegen
     - ReactCommon/turbomodule/bridging
     - ReactCommon/turbomodule/core
-    - ShopifyCheckoutKit (~> 4.0.0-alpha.4)
-    - ShopifyCheckoutKit/AcceleratedCheckouts (~> 4.0.0-alpha.4)
+    - ShopifyCheckoutKit (~> 4.0.0-alpha.5)
+    - ShopifyCheckoutKit/AcceleratedCheckouts (~> 4.0.0-alpha.5)
     - SocketRocket
     - Yoga
   - RNVectorIcons (10.3.0):
@@ -2638,11 +2638,11 @@ PODS:
     - ReactCommon/turbomodule/core
     - SocketRocket
     - Yoga
-  - ShopifyCheckoutKit (4.0.0-alpha.4):
-    - ShopifyCheckoutKit/Core (= 4.0.0-alpha.4)
-  - ShopifyCheckoutKit/AcceleratedCheckouts (4.0.0-alpha.4):
+  - ShopifyCheckoutKit (4.0.0-alpha.5):
+    - ShopifyCheckoutKit/Core (= 4.0.0-alpha.5)
+  - ShopifyCheckoutKit/AcceleratedCheckouts (4.0.0-alpha.5):
     - ShopifyCheckoutKit/Core
-  - ShopifyCheckoutKit/Core (4.0.0-alpha.4)
+  - ShopifyCheckoutKit/Core (4.0.0-alpha.5)
   - SocketRocket (0.7.1)
   - Yoga (0.0.0)
 
@@ -2996,9 +2996,9 @@ SPEC CHECKSUMS:
   RNGestureHandler: eeb622199ef1fb3a076243131095df1c797072f0
   RNReanimated: 237d420b7bb4378ef1dacc7d7a5c674fddb4b5d2
   RNScreens: 3fc29af06302e1f1c18a7829fe57cbc2c0259912
-  RNShopifyCheckoutKit: 2f123d00c3b48120f8e02a3c1c650db61caec677
+  RNShopifyCheckoutKit: 25f8126109e2af64a90429370ef0436a2871fbdc
   RNVectorIcons: be4d047a76ad307ffe54732208fb0498fcb8477f
-  ShopifyCheckoutKit: 95b6402d901c45c2b2b3fc1182a6fe735f1b7c54
+  ShopifyCheckoutKit: 7874c8866e6c889d86194398c97e00388111d972
   SocketRocket: d4aabe649be1e368d1318fdf28a022d714d65748
   Yoga: a742cc68e8366fcfc681808162492bc0aa7a9498
 
diff --git a/platforms/react-native/test/rct-integration-app/Podfile.lock b/platforms/react-native/test/rct-integration-app/Podfile.lock
index 4a22c56fc..08006511b 100644
--- a/platforms/react-native/test/rct-integration-app/Podfile.lock
+++ b/platforms/react-native/test/rct-integration-app/Podfile.lock
@@ -2149,15 +2149,15 @@ PODS:
     - ReactCodegen
     - ReactCommon/turbomodule/bridging
     - ReactCommon/turbomodule/core
-    - ShopifyCheckoutKit (~> 4.0.0-alpha.4)
-    - ShopifyCheckoutKit/AcceleratedCheckouts (~> 4.0.0-alpha.4)
+    - ShopifyCheckoutKit (~> 4.0.0-alpha.5)
+    - ShopifyCheckoutKit/AcceleratedCheckouts (~> 4.0.0-alpha.5)
     - SocketRocket
     - Yoga
-  - ShopifyCheckoutKit (4.0.0-alpha.4):
-    - ShopifyCheckoutKit/Core (= 4.0.0-alpha.4)
-  - ShopifyCheckoutKit/AcceleratedCheckouts (4.0.0-alpha.4):
+  - ShopifyCheckoutKit (4.0.0-alpha.5):
+    - ShopifyCheckoutKit/Core (= 4.0.0-alpha.5)
+  - ShopifyCheckoutKit/AcceleratedCheckouts (4.0.0-alpha.5):
     - ShopifyCheckoutKit/Core
-  - ShopifyCheckoutKit/Core (4.0.0-alpha.4)
+  - ShopifyCheckoutKit/Core (4.0.0-alpha.5)
   - SocketRocket (0.7.1)
   - Yoga (0.0.0)
 
@@ -2464,8 +2464,8 @@ SPEC CHECKSUMS:
   ReactAppDependencyProvider: 8df342c127fd0c1e30e8b9f71ff814c22414a7c0
   ReactCodegen: 3ba2a79bc32ff858814c17ade10931b33b09dcf4
   ReactCommon: 592ef441605638b95e533653259254b4bd35ff4f
-  RNShopifyCheckoutKit: 2f123d00c3b48120f8e02a3c1c650db61caec677
-  ShopifyCheckoutKit: 95b6402d901c45c2b2b3fc1182a6fe735f1b7c54
+  RNShopifyCheckoutKit: 25f8126109e2af64a90429370ef0436a2871fbdc
+  ShopifyCheckoutKit: 7874c8866e6c889d86194398c97e00388111d972
   SocketRocket: d4aabe649be1e368d1318fdf28a022d714d65748
   Yoga: a742cc68e8366fcfc681808162492bc0aa7a9498
 
diff --git a/platforms/react-native/test/rct-integration-app/RCTIntegrationAppTests/ShopifyCheckoutKitTests.swift b/platforms/react-native/test/rct-integration-app/RCTIntegrationAppTests/ShopifyCheckoutKitTests.swift
index 027e8c8d9..c79589600 100644
--- a/platforms/react-native/test/rct-integration-app/RCTIntegrationAppTests/ShopifyCheckoutKitTests.swift
+++ b/platforms/react-native/test/rct-integration-app/RCTIntegrationAppTests/ShopifyCheckoutKitTests.swift
@@ -22,6 +22,7 @@ class ShopifyCheckoutKitTests: XCTestCase {
         ShopifyCheckoutKit.configuration.closeButtonTintColor = nil
         ShopifyCheckoutKit.configuration.logLevel = LogLevel.warn
         ShopifyCheckoutKit.configuration.preloading.enabled = true
+        ShopifyCheckoutKit.configuration.allowedMessageOrigins = []
     }
 
     private func getShopifyCheckoutKit() -> RCTShopifyCheckoutKit {
@@ -99,6 +100,21 @@ class ShopifyCheckoutKitTests: XCTestCase {
         XCTAssertEqual(result?["title"] as? String, "Custom Checkout")
     }
 
+    func testAllowedMessageOriginsRoundTrip() {
+        shopifyCheckoutKit.setConfig(["allowedMessageOrigins": ["https://example.com", "https://*.example.com"]])
+
+        XCTAssertEqual(
+            ShopifyCheckoutKit.configuration.allowedMessageOrigins,
+            ["https://example.com", "https://*.example.com"]
+        )
+
+        let result = shopifyCheckoutKit.getConfig() as? [String: Any]
+        XCTAssertEqual(
+            result?["allowedMessageOrigins"] as? [String],
+            ["https://example.com", "https://*.example.com"]
+        )
+    }
+
     func testConfigureWithInvalidColors() {
         let configuration: [AnyHashable: Any] = [
             "colors": [