diff --git a/apps/api/app/api/routes/generation_preview.py b/apps/api/app/api/routes/generation_preview.py
index 12270525c..2867b084c 100755
--- a/apps/api/app/api/routes/generation_preview.py
+++ b/apps/api/app/api/routes/generation_preview.py
@@ -213,7 +213,7 @@ def get_preview_generation_task(
 
     # 权限校验：任务必须属于当前用户
     task_user_id = getattr(task, "created_by_user_id", "") or ""
-    if task_user_id and task_user_id != authenticated_user.user.id:
+    if not task_user_id or task_user_id != authenticated_user.user.id:
         raise HTTPException(status_code=403, detail="无权访问该任务")
 
     # 校验是否为预览任务
diff --git a/apps/worker/worker_app/tasks/generation.py b/apps/worker/worker_app/tasks/generation.py
index d697368f6..e2eb61897 100755
--- a/apps/worker/worker_app/tasks/generation.py
+++ b/apps/worker/worker_app/tasks/generation.py
@@ -1056,8 +1056,9 @@ def _render_video(
     # 确保输出分辨率配置存在
     # 优先级：用户指定 > 模板配置 > 默认 1280x720
     # 预览模式：强制 854x480 + 低码率
-    plan_cfg = virtual_plan.config or {}
-    export_cfg = plan_cfg.get("export", {}) or {}
+    # 注意：必须拷贝字典，避免预览模式修改污染源对象（模板配置）
+    plan_cfg = dict(virtual_plan.config or {})
+    export_cfg = dict(plan_cfg.get("export", {}) or {})
     if is_preview:
         # 预览模式强制 480p + 低码率
         export_cfg["resolution"] = "854x480"
diff --git a/tests/unit/test_generation_preview.py b/tests/unit/test_generation_preview.py
index 06b7f839a..ca05fca75 100755
--- a/tests/unit/test_generation_preview.py
+++ b/tests/unit/test_generation_preview.py
@@ -945,6 +945,26 @@ class TestGetPreviewRoute:
         assert resp.status == "pending"
         assert resp.is_preview is True
 
+    def test_empty_user_id_denied(self):
+        """任务 created_by_user_id 为空 → 403（防止越权）"""
+        repo = MagicMock()
+        vid_repo = MagicMock()
+        task = _make_task()
+        task.created_by_user_id = ""  # 空字符串
+
+        from fastapi import HTTPException
+
+        with patch("app.api.routes.generation_preview.GetGenerationTaskUseCase") as MockUC:
+            MockUC.return_value.execute.return_value = task
+            with pytest.raises(HTTPException) as exc_info:
+                get_preview_generation_task(
+                    task_id="preview_task_001",
+                    authenticated_user=_make_user(),
+                    generation_task_repository=repo,
+                    generated_video_repository=vid_repo,
+                )
+            assert exc_info.value.status_code == 403
+
     def test_get_completed_task_with_videos(self):
         """查询 completed 状态任务，返回视频列表"""
         repo = MagicMock()
@@ -980,11 +1000,12 @@ class TestWorkerPreviewResolution:
 
     def test_preview_mode_forces_480p(self):
         """预览模式强制 854x480 + 1M 码率"""
-        # 模拟 worker 中 export_cfg 逻辑
+        # 模拟 worker 中 export_cfg 逻辑（与实际代码一致，使用 dict 拷贝）
         is_preview = True
         resolution = "1920x1080"  # 用户指定的分辨率应被忽略
-        plan_cfg = {"export": {"resolution": "1280x720", "bitrate": "5M"}}
-        export_cfg = plan_cfg.get("export", {}) or {}
+        original_config = {"export": {"resolution": "1280x720", "bitrate": "5M"}}
+        plan_cfg = dict(original_config)
+        export_cfg = dict(plan_cfg.get("export", {}) or {})
 
         if is_preview:
             export_cfg["resolution"] = "854x480"
@@ -992,15 +1013,19 @@ class TestWorkerPreviewResolution:
         elif resolution:
             export_cfg["resolution"] = resolution
 
+        plan_cfg["export"] = export_cfg
+
         assert export_cfg["resolution"] == "854x480"
         assert export_cfg["bitrate"] == "1M"
+        # 验证原始配置未被污染
+        assert original_config["export"]["resolution"] == "1280x720"
 
     def test_non_preview_uses_user_resolution(self):
         """非预览模式使用用户指定分辨率"""
         is_preview = False
         resolution = "1920x1080"
-        plan_cfg = {"export": {"resolution": "1280x720"}}
-        export_cfg = plan_cfg.get("export", {}) or {}
+        plan_cfg = dict({"export": {"resolution": "1280x720"}})
+        export_cfg = dict(plan_cfg.get("export", {}) or {})
 
         if is_preview:
             export_cfg["resolution"] = "854x480"
@@ -1014,8 +1039,8 @@ class TestWorkerPreviewResolution:
         """非预览模式且用户未指定分辨率，使用模板配置"""
         is_preview = False
         resolution = ""
-        plan_cfg = {"export": {"resolution": "1280x720"}}
-        export_cfg = plan_cfg.get("export", {}) or {}
+        plan_cfg = dict({"export": {"resolution": "1280x720"}})
+        export_cfg = dict(plan_cfg.get("export", {}) or {})
 
         if is_preview:
             export_cfg["resolution"] = "854x480"
@@ -1030,8 +1055,8 @@ class TestWorkerPreviewResolution:
     def test_preview_mode_empty_export_cfg(self):
         """预览模式且模板无 export 配置"""
         is_preview = True
-        plan_cfg = {}
-        export_cfg = plan_cfg.get("export", {}) or {}
+        plan_cfg = dict({})
+        export_cfg = dict(plan_cfg.get("export", {}) or {})
 
         if is_preview:
             export_cfg["resolution"] = "854x480"