diff --git a/backend/problem/views/admin.py b/backend/problem/views/admin.py
index ef48887fa..3f02af3ef 100644
--- a/backend/problem/views/admin.py
+++ b/backend/problem/views/admin.py
@@ -245,6 +245,8 @@ def get(self, request):
             ensure_created_by(problem.contest, request.user)
         elif problem.assignment:
             ensure_created_by(problem.assignment, request.user)
+        elif problem.course:
+            ensure_created_by(problem.course, request.user)
         else:
             ensure_created_by(problem, request.user)
 
diff --git a/backend/problem/views/oj.py b/backend/problem/views/oj.py
index e87ebcc49..004c1b0a6 100644
--- a/backend/problem/views/oj.py
+++ b/backend/problem/views/oj.py
@@ -78,7 +78,7 @@ def get(self, request):
         if problem_id:
             try:
                 problem = Problem.objects.select_related("created_by") \
-                    .get(_id=problem_id, contest_id__isnull=True, assignment_id__isnull=True, visible=True)
+                    .get(_id=problem_id, contest_id__isnull=True, assignment_id__isnull=True, course_id__isnull=True, visible=True)
                 problem_data = ProblemSerializer(problem).data
                 self._add_problem_status(request, problem_data)
                 return self.success(problem_data)
@@ -89,7 +89,7 @@ def get(self, request):
         if not limit:
             return self.error("Limit is needed")
 
-        problems = Problem.objects.select_related("created_by").filter(contest_id__isnull=True, assignment_id__isnull=True, visible=True)
+        problems = Problem.objects.select_related("created_by").filter(contest_id__isnull=True, assignment_id__isnull=True, course_id__isnull=True, visible=True)
         # filter by label
         tag_text = request.GET.get("tag")
         if tag_text:
diff --git a/backend/problem/views/professor.py b/backend/problem/views/professor.py
index b94cba883..af1334dcf 100644
--- a/backend/problem/views/professor.py
+++ b/backend/problem/views/professor.py
@@ -271,7 +271,7 @@ def get(self, request):
         except Course.DoesNotExist:
             return self.error("Course does not exist")
 
-        problems = Problem.objects.filter(course=course).order_by("create_time")
+        problems = Problem.objects.filter(course=course).order_by("-create_time")
         return self.success(self.paginate_data(request, problems, ProblemCourseProfessorSerializer))
 
     @swagger_auto_schema(
diff --git a/backend/submission/views.py b/backend/submission/views.py
index a13368b91..c91f53d9d 100644
--- a/backend/submission/views.py
+++ b/backend/submission/views.py
@@ -4,6 +4,7 @@
 from drf_yasg import openapi
 
 from assignment.models import Assignment
+from course.models import Course
 from contest.models import ContestStatus, ContestRuleType
 from judge.tasks import judge_task
 from options.options import SysOptions