diff --git a/dev/src/main/java/com/google/adk/web/config/AdkWebCorsProperties.java b/dev/src/main/java/com/google/adk/web/config/AdkWebCorsProperties.java
index c96dce91e..0343f7d58 100644
--- a/dev/src/main/java/com/google/adk/web/config/AdkWebCorsProperties.java
+++ b/dev/src/main/java/com/google/adk/web/config/AdkWebCorsProperties.java
@@ -34,7 +34,7 @@ public record AdkWebCorsProperties(
 
   public AdkWebCorsProperties {
     mapping = mapping != null ? mapping : "/**";
-    origins = origins != null && !origins.isEmpty() ? origins : List.of("*");
+    origins = origins != null ? origins : List.of();
     methods =
         methods != null && !methods.isEmpty()
             ? methods
diff --git a/dev/src/main/java/com/google/adk/web/websocket/WebSocketConfig.java b/dev/src/main/java/com/google/adk/web/websocket/WebSocketConfig.java
index a17d72aff..a5b9043fc 100644
--- a/dev/src/main/java/com/google/adk/web/websocket/WebSocketConfig.java
+++ b/dev/src/main/java/com/google/adk/web/websocket/WebSocketConfig.java
@@ -21,6 +21,7 @@
 import org.springframework.context.annotation.Configuration;
 import org.springframework.web.socket.config.annotation.EnableWebSocket;
 import org.springframework.web.socket.config.annotation.WebSocketConfigurer;
+import org.springframework.web.socket.config.annotation.WebSocketHandlerRegistration;
 import org.springframework.web.socket.config.annotation.WebSocketHandlerRegistry;
 
 /** Configuration class for WebSocket handling. */
@@ -40,8 +41,10 @@ public WebSocketConfig(
 
   @Override
   public void registerWebSocketHandlers(WebSocketHandlerRegistry registry) {
-    registry
-        .addHandler(liveWebSocketHandler, "/run_live")
-        .setAllowedOrigins(corsProperties.origins().toArray(new String[0]));
+    WebSocketHandlerRegistration registration =
+        registry.addHandler(liveWebSocketHandler, "/run_live");
+    if (!corsProperties.origins().isEmpty()) {
+      registration.setAllowedOrigins(corsProperties.origins().toArray(String[]::new));
+    }
   }
 }
diff --git a/dev/src/test/java/com/google/adk/web/config/AdkWebCorsConfigTest.java b/dev/src/test/java/com/google/adk/web/config/AdkWebCorsConfigTest.java
new file mode 100644
index 000000000..8b1e26170
--- /dev/null
+++ b/dev/src/test/java/com/google/adk/web/config/AdkWebCorsConfigTest.java
@@ -0,0 +1,57 @@
+/*
+ * Copyright 2026 Google LLC
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.google.adk.web.config;
+
+import static com.google.common.truth.Truth.assertThat;
+
+import java.util.List;
+import org.junit.jupiter.api.Test;
+import org.springframework.mock.web.MockHttpServletRequest;
+import org.springframework.web.cors.CorsConfiguration;
+import org.springframework.web.cors.CorsConfigurationSource;
+
+class AdkWebCorsConfigTest {
+
+  private final AdkWebCorsConfig config = new AdkWebCorsConfig();
+
+  @Test
+  void defaultCorsConfigurationDoesNotAllowArbitraryOrigins() {
+    CorsConfiguration corsConfiguration =
+        getCorsConfiguration(new AdkWebCorsProperties(null, null, null, null, false, 0));
+
+    assertThat(corsConfiguration.checkOrigin("https://attacker.example")).isNull();
+  }
+
+  @Test
+  void explicitCorsOriginsAreStillAllowed() {
+    CorsConfiguration corsConfiguration =
+        getCorsConfiguration(
+            new AdkWebCorsProperties(null, List.of("http://localhost:3000"), null, null, false, 0));
+
+    assertThat(corsConfiguration.checkOrigin("http://localhost:3000"))
+        .isEqualTo("http://localhost:3000");
+    assertThat(corsConfiguration.checkOrigin("https://attacker.example")).isNull();
+  }
+
+  private CorsConfiguration getCorsConfiguration(AdkWebCorsProperties properties) {
+    CorsConfigurationSource source = config.corsConfigurationSource(properties);
+    CorsConfiguration corsConfiguration =
+        source.getCorsConfiguration(new MockHttpServletRequest("POST", "/run"));
+    assertThat(corsConfiguration).isNotNull();
+    return corsConfiguration;
+  }
+}
diff --git a/dev/src/test/java/com/google/adk/web/websocket/WebSocketConfigTest.java b/dev/src/test/java/com/google/adk/web/websocket/WebSocketConfigTest.java
new file mode 100644
index 000000000..6fa3482bf
--- /dev/null
+++ b/dev/src/test/java/com/google/adk/web/websocket/WebSocketConfigTest.java
@@ -0,0 +1,59 @@
+/*
+ * Copyright 2026 Google LLC
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.google.adk.web.websocket;
+
+import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.never;
+import static org.mockito.Mockito.verify;
+import static org.mockito.Mockito.when;
+
+import com.google.adk.web.config.AdkWebCorsProperties;
+import java.util.List;
+import org.junit.jupiter.api.Test;
+import org.springframework.web.socket.config.annotation.WebSocketHandlerRegistration;
+import org.springframework.web.socket.config.annotation.WebSocketHandlerRegistry;
+
+class WebSocketConfigTest {
+
+  @Test
+  void defaultWebSocketConfigurationDoesNotAllowArbitraryOrigins() {
+    LiveWebSocketHandler handler = mock(LiveWebSocketHandler.class);
+    WebSocketHandlerRegistry registry = mock(WebSocketHandlerRegistry.class);
+    WebSocketHandlerRegistration registration = mock(WebSocketHandlerRegistration.class);
+    when(registry.addHandler(handler, "/run_live")).thenReturn(registration);
+
+    new WebSocketConfig(handler, new AdkWebCorsProperties(null, null, null, null, false, 0))
+        .registerWebSocketHandlers(registry);
+
+    verify(registration, never()).setAllowedOrigins("*");
+  }
+
+  @Test
+  void explicitCorsOriginsAreAppliedToWebSocketEndpoint() {
+    LiveWebSocketHandler handler = mock(LiveWebSocketHandler.class);
+    WebSocketHandlerRegistry registry = mock(WebSocketHandlerRegistry.class);
+    WebSocketHandlerRegistration registration = mock(WebSocketHandlerRegistration.class);
+    when(registry.addHandler(handler, "/run_live")).thenReturn(registration);
+
+    new WebSocketConfig(
+            handler,
+            new AdkWebCorsProperties(null, List.of("http://localhost:3000"), null, null, false, 0))
+        .registerWebSocketHandlers(registry);
+
+    verify(registration).setAllowedOrigins("http://localhost:3000");
+  }
+}