From dcf0385a872848214045e03b42a85c2413e38cb8 Mon Sep 17 00:00:00 2001
From: JakkrapartXD <jakkrapart_in66@live.rmutl.ac.th>
Date: Thu, 22 Jan 2026 16:22:33 +0700
Subject: [PATCH] protech

---
 Backend/src/services/ChaptersLesson.service.ts | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/Backend/src/services/ChaptersLesson.service.ts b/Backend/src/services/ChaptersLesson.service.ts
index 5483ff81..57462d69 100644
--- a/Backend/src/services/ChaptersLesson.service.ts
+++ b/Backend/src/services/ChaptersLesson.service.ts
@@ -182,6 +182,10 @@ export class ChaptersLessonService {
             if (!currentChapter) {
                 throw new NotFoundError('Chapter not found');
             }
+            // Validate chapter belongs to the specified course
+            if (currentChapter.course_id !== course_id) {
+                throw new NotFoundError('Chapter not found in this course');
+            }
             const oldSortOrder = currentChapter.sort_order;
 
             // If same position, no need to reorder