"Checking this file with your organizations's security policies..." in Chrome prevents `pickFiles`

[dcharkes]

With security policies the file uploads don't work.

    final result = await FilePicker.platform.pickFiles(
      type: FileType.custom,
      allowedExtensions: ['json'],
      withData: true,
    );
    // result returns `null` _before_ the dialog in the browser disappears.

Platform

• Android
• iOS
• Web
• Desktop

Platform OS version
MacOS, in the Chrome browser.

How are you picking?

    final result = await FilePicker.platform.pickFiles(
      type: FileType.custom,
      allowedExtensions: ['json'],
      withData: true,
    );

Details to reproduce the issue
Write a Flutter app and run it with flutter run -d chrome.

The app functions correctly on Firefox.

And uploading the file in other UIs works fine after after the securities dialog disappears.

Error Log

$ flutter run -d chrome
This application is not configured to build on the web.
To add web support to a project, run `flutter create .`.
Launching lib/main.dart on Chrome in debug mode...
Waiting for connection from debug service on Chrome...              9.2s

Flutter run key commands.
r Hot reload. 🔥🔥🔥
R Hot restart.
h List all available interactive commands.
d Detach (terminate "flutter run" but leave application running).
c Clear the screen
q Quit (terminate the application on the device).

This app is linked to the debug service: ws://127.0.0.1:49175/uijiThBbEKY=/ws
Debug service listening on ws://127.0.0.1:49175/uijiThBbEKY=/ws
A Dart VM Service on Chrome is available at: http://127.0.0.1:49175/uijiThBbEKY=
The Flutter DevTools debugger and profiler on Chrome is available at:
http://127.0.0.1:49175/uijiThBbEKY=/devtools/?uri=ws://127.0.0.1:49175/uijiThBbEKY=/ws
Starting application from main method in: org-dartlang-app:/web_entrypoint.dart.
A message on the flutter/lifecycle channel was discarded before it could be handled.
This happens when a plugin sends messages to the framework side before the framework has had an opportunity to register a listener.
See the ChannelBuffers API documentation for details on how to configure the channel to expect more messages, or to expect messages
to get discarded:
  https://api.flutter.dev/flutter/dart-ui/ChannelBuffers-class.html
A message on the flutter/lifecycle channel was discarded before it could be handled.
This happens when a plugin sends messages to the framework side before the framework has had an opportunity to register a listener.
See the ChannelBuffers API documentation for details on how to configure the channel to expect more messages, or to expect messages
to get discarded:
  https://api.flutter.dev/flutter/dart-ui/ChannelBuffers-class.html

Browser console:

DDC is about to load 1/2 scripts with pool size = 1000
ddc_module_loader.js:1015 DDC is about to load 736/736 scripts with pool size = 1000
 This app is linked to the debug service: ws://127.0.0.1:49175/uijiThBbEKY=/ws
ddc_module_loader.js:1583 Starting application from main method in: org-dartlang-app:/web_entrypoint.dart.
dom.dart:189 A message on the flutter/lifecycle channel was discarded before it could be handled.
This happens when a plugin sends messages to the framework side before the framework has had an opportunity to register a listener. See the ChannelBuffers API documentation for details on how to configure the channel to expect more messages, or to expect messages to get discarded:
  https://api.flutter.dev/flutter/dart-ui/ChannelBuffers-class.html
DomConsole$124warn @ dom.dart:189
(anonymous) @ dom.dart:189
(anonymous) @ channel_buffers.dart:138
push @ channel_buffers.dart:146
invokeOnPlatformMessage @ platform_dispatcher.dart:418
[_setAppLifecycleState] @ platform_dispatcher.dart:1190
tear @ operations.dart:118
onAppLifecycleStateChange @ app_lifecycle_state.dart:50
(anonymous) @ app_lifecycle_state.dart:94
runUnary @ zone.dart:962
(anonymous) @ zone.dart:917
_callDartFunctionFast1 @ js_allow_interop_patch.dart:224
ret @ js_allow_interop_patch.dart:84Understand this warning
dom.dart:189 A message on the flutter/lifecycle channel was discarded before it could be handled.
This happens when a plugin sends messages to the framework side before the framework has had an opportunity to register a listener. See the ChannelBuffers API documentation for details on how to configure the channel to expect more messages, or to expect messages to get discarded:
  https://api.flutter.dev/flutter/dart-ui/ChannelBuffers-class.html

Flutter Version details

$ flutter doctor -v
[✓] Flutter (Channel master, 3.39.0-1.0.pre-238, on macOS 15.7.2 24G325 darwin-arm64, locale en-US) [1,541ms]
    • Flutter version 3.39.0-1.0.pre-238 on channel master at /Users/dacoharkes/src/flutter/flutter
    • Upstream repository https://github.com/flutter/flutter.git
    • Framework revision 9c6e1e319f (32 hours ago), 2025-11-21 06:58:41 -0500
    • Engine revision 9c6e1e319f
    • Dart version 3.11.0 (build 3.11.0-160.0.dev)
    • DevTools version 2.52.0
    • Feature flags: enable-web, enable-linux-desktop, enable-macos-desktop, enable-windows-desktop, enable-android, enable-ios,
      cli-animations, enable-native-assets, omit-legacy-version-file, enable-lldb-debugging, enable-uiscene-migration

[✓] Android toolchain - develop for Android devices (Android SDK version 36.0.0) [1,421ms]
    • Android SDK at /Users/dacoharkes/Library/Android/sdk
    • Emulator version 35.5.10.0 (build_id 13402964) (CL:N/A)
    • Platform android-36, build-tools 36.0.0
    • ANDROID_HOME = /Users/dacoharkes/Library/Android/sdk
    • Java binary at: /Applications/Android Studio.app/Contents/jbr/Contents/Home/bin/java
      This is the JDK bundled with the latest Android Studio installation on this machine.
      To manually set the JDK path, use: `flutter config --jdk-dir="path/to/jdk"`.
    • Java version OpenJDK Runtime Environment (build 21.0.6+-13368085-b895.109)
    • All Android licenses accepted.

[✓] Xcode - develop for iOS and macOS (Xcode 16.4) [563ms]
    • Xcode at /Applications/Xcode.app/Contents/Developer
    • Build 16F6
    • CocoaPods version 1.16.2

[✓] Chrome - develop for the web [6ms]
    • Chrome at /Applications/Google Chrome.app/Contents/MacOS/Google Chrome

[✓] Connected device (2 available) [5.7s]
    • macOS (desktop) • macos  • darwin-arm64   • macOS 15.7.2 24G325 darwin-arm64
    • Chrome (web)    • chrome • web-javascript • Google Chrome 142.0.7444.176
    ! Error: Browsing on the local area network for Daco’s iPhone. Ensure the device is unlocked and attached with a cable or
      associated with the same local area network as this Mac.
      The device must be opted into Developer Mode to connect wirelessly. (code -27)

[✓] Network resources [899ms]
    • All expected network resources are available.

• No issues found!

Additional context

File picker version:

  file_picker:
    dependency: "direct main"
    description:
      name: file_picker
      sha256: "7872545770c277236fd32b022767576c562ba28366204ff1a5628853cf8f2200"
      url: "https://pub.dev"
    source: hosted
    version: "10.3.7"