diff --git a/apps/oss/tests.py b/apps/oss/tests.py
index 4703c42b873..a7b7c4283af 100644
--- a/apps/oss/tests.py
+++ b/apps/oss/tests.py
@@ -1,7 +1,12 @@
+from unittest import mock
+
 from django.test import SimpleTestCase
 from django.urls import resolve
 
+from common.exception.app_exception import AppUnauthorizedFailed
+from knowledge.models import FileSourceType
 from maxkb.const import CONFIG
+from oss.serializers.file import auth
 from oss.views import FileRetrievalView, FileView, GetUrlView
 
 
@@ -52,3 +57,102 @@ def test_get_url_retrieval_routes_pass_application_id(self):
             'chat_oss_retrieval',
             {'application_id': 'application-id'},
         )
+
+
+class FileAuthTestCase(SimpleTestCase):
+    """Regression tests for anonymous retrieval of APPLICATION-source files."""
+
+    @staticmethod
+    def _make_file(source_type, source_id, meta=None):
+        file = mock.Mock()
+        file.id = 'f0000000-0000-0000-0000-000000000001'
+        file.source_type = source_type
+        file.source_id = source_id
+        file.meta = meta or {}
+        return file
+
+    def test_application_file_without_token_is_denied(self):
+        """A visitor-created APPLICATION file with no chat_id must not be publicly retrievable."""
+        file = self._make_file(FileSourceType.APPLICATION, 'application-1')
+        with mock.patch('oss.serializers.file.CONFIG', {'FILE_AUTH': '1'}), \
+                mock.patch('oss.serializers.file.QuerySet') as qs:
+            qs.return_value.filter.return_value.exists.return_value = False
+            with self.assertRaises(AppUnauthorizedFailed):
+                auth(file, None)
+
+    def test_public_temporary_file_does_not_require_token(self):
+        """Temporary/public source types remain anonymously retrievable."""
+        file = self._make_file(FileSourceType.TEMPORARY_120_MINUTE, FileSourceType.TEMPORARY_120_MINUTE.value)
+        with mock.patch('oss.serializers.file.CONFIG', {'FILE_AUTH': '1'}):
+            # It should return without raising.
+            self.assertIsNone(auth(file, None))
+
+
+class FileUploadPermissionTestCase(SimpleTestCase):
+    """The /oss/file upload endpoint must not let chat/anon clients bind files to protected sources."""
+
+    @staticmethod
+    def _chat_request(source_type, source_id):
+        request = mock.Mock()
+        request.user = None
+        request.auth = mock.Mock()
+        request.auth.chat_user_id = 'chat-user-1'
+        request.data = {'source_type': source_type, 'source_id': source_id}
+        request.FILES = {'file': mock.Mock()}
+        request.META = {}
+        request.path = '/chat/api/oss/file'
+        request.query_params = {}
+        return request
+
+    def test_chat_upload_binding_to_application_is_denied(self):
+        request = self._chat_request(FileSourceType.APPLICATION.value, 'application-1')
+        with mock.patch('common.log.log.Log'):
+            with self.assertRaises(AppUnauthorizedFailed):
+                FileView().post(request)
+
+    def test_chat_upload_binding_to_chat_is_allowed(self):
+        request = self._chat_request(FileSourceType.CHAT.value, 'chat-1')
+        with mock.patch('common.log.log.Log'), \
+                mock.patch('oss.views.file.QuerySet') as qs, \
+                mock.patch('oss.views.file.FileSerializer') as serializer_cls:
+            qs.return_value.filter.return_value.first.return_value = mock.Mock()
+            serializer_cls.return_value.upload.return_value = './oss/file/1'
+            response = FileView().post(request)
+        self.assertEqual(response.status_code, 200)
+
+    def test_chat_upload_binding_to_foreign_chat_is_denied(self):
+        request = self._chat_request(FileSourceType.CHAT.value, 'foreign-chat')
+        with mock.patch('common.log.log.Log'), \
+                mock.patch('oss.views.file.QuerySet') as qs:
+            qs.return_value.filter.return_value.first.return_value = None
+            with self.assertRaises(AppUnauthorizedFailed):
+                FileView().post(request)
+
+    def test_system_user_upload_binding_to_application_is_allowed(self):
+        request = mock.Mock()
+        request.user = mock.Mock()
+        request.user.id = 'user-1'
+        request.data = {'source_type': FileSourceType.APPLICATION.value, 'source_id': 'application-1'}
+        request.FILES = {'file': mock.Mock()}
+        request.META = {}
+        request.path = '/admin/api/oss/file'
+        request.query_params = {}
+        with mock.patch('common.log.log.Log'), \
+                mock.patch('oss.views.file.FileSerializer') as serializer_cls:
+            serializer_cls.return_value.upload.return_value = './oss/file/1'
+            response = FileView().post(request)
+        self.assertEqual(response.status_code, 200)
+
+    def test_logged_in_user_on_chat_path_cannot_bind_to_application(self):
+        """Even a logged-in user must not bind files to protected sources via the /chat path."""
+        request = mock.Mock()
+        request.user = mock.Mock()
+        request.user.id = 'user-1'
+        request.data = {'source_type': FileSourceType.APPLICATION.value, 'source_id': 'application-1'}
+        request.FILES = {'file': mock.Mock()}
+        request.META = {}
+        request.path = '/chat/api/oss/file'
+        request.query_params = {}
+        with mock.patch('common.log.log.Log'):
+            with self.assertRaises(AppUnauthorizedFailed):
+                FileView().post(request)