diff --git a/packages/devtools_shared/CHANGELOG.md b/packages/devtools_shared/CHANGELOG.md
index 0f1f770d1a9..f6fa2bc2db5 100644
--- a/packages/devtools_shared/CHANGELOG.md
+++ b/packages/devtools_shared/CHANGELOG.md
@@ -3,6 +3,11 @@ Copyright 2025 The Flutter Authors
 Use of this source code is governed by a BSD-style license that can be
 found in the LICENSE file or at https://developers.google.com/open-source/licenses/bsd.
 -->
+# 13.0.2
+* Validate the `devtoolsOptionsUri` query parameter in the extension enabled
+  state handler so it must be a `file:` URI named `devtools_options.yaml`,
+  preventing arbitrary file writes by the DevTools server process.
+
 # 13.0.1
 * Handle null values for `FlutterStore.flutterClientId`.
 
diff --git a/packages/devtools_shared/lib/src/server/handlers/_devtools_extensions.dart b/packages/devtools_shared/lib/src/server/handlers/_devtools_extensions.dart
index f7c63671630..e87e2704d23 100644
--- a/packages/devtools_shared/lib/src/server/handlers/_devtools_extensions.dart
+++ b/packages/devtools_shared/lib/src/server/handlers/_devtools_extensions.dart
@@ -80,6 +80,27 @@ extension _ExtensionsApiHandler on Never {
     final devtoolsOptionsFileUriString =
         queryParams[ExtensionsApi.devtoolsOptionsUriPropertyName]!;
     final devtoolsOptionsFileUri = Uri.parse(devtoolsOptionsFileUriString);
+
+    // Validate that the URI is a local file URI whose file name is exactly
+    // 'devtools_options.yaml'. Accepting arbitrary URIs from the query string
+    // would allow an untrusted caller to create or overwrite any file writable
+    // by the DevTools server process. Resolving the name through
+    // `Uri.toFilePath()` + `p.basename` handles both '/' and '\' path
+    // separators, so the check holds for Windows file URIs as well. Requiring
+    // an empty host rejects UNC paths (e.g. `file://server/share/...`) and
+    // keeps `toFilePath()` from throwing on a non-local authority.
+    final isFileUri = devtoolsOptionsFileUri.scheme == 'file' &&
+        devtoolsOptionsFileUri.host.isEmpty;
+    final fileName = isFileUri
+        ? p.basename(devtoolsOptionsFileUri.toFilePath())
+        : '';
+    if (!isFileUri || fileName != 'devtools_options.yaml') {
+      return api.badRequest(
+        'Invalid devtoolsOptionsUri: must be a file: URI named '
+        "'devtools_options.yaml'.",
+      );
+    }
+
     final extensionName = queryParams[ExtensionsApi.extensionNamePropertyName]!;
 
     final activate = queryParams[ExtensionsApi.enabledStatePropertyName];
diff --git a/packages/devtools_shared/lib/src/server/server_api.dart b/packages/devtools_shared/lib/src/server/server_api.dart
index f9b50724845..cc41fb0d9e7 100644
--- a/packages/devtools_shared/lib/src/server/server_api.dart
+++ b/packages/devtools_shared/lib/src/server/server_api.dart
@@ -11,6 +11,7 @@ import 'dart:io';
 import 'package:collection/collection.dart';
 import 'package:dtd/dtd.dart';
 import 'package:meta/meta.dart';
+import 'package:path/path.dart' as p;
 import 'package:shelf/shelf.dart' as shelf;
 import 'package:vm_service/vm_service.dart';
 
diff --git a/packages/devtools_shared/pubspec.yaml b/packages/devtools_shared/pubspec.yaml
index dce148c2109..585ad854798 100644
--- a/packages/devtools_shared/pubspec.yaml
+++ b/packages/devtools_shared/pubspec.yaml
@@ -4,7 +4,7 @@
 name: devtools_shared
 description: Package of shared Dart structures between devtools_app, dds, and other tools.
 
-version: 13.0.1
+version: 13.0.2
 
 repository: https://github.com/flutter/devtools/tree/master/packages/devtools_shared