Fix security, transaction, and badge issues from final review

- Validate file URLs against S3 prefix in messages route (Fix 1)
- Guard attachment hrefs with https:// check in QuestionThread and QuestionSplitView (Fix 2)
- Wrap message create + updatedAt bump in prisma.$transaction (Fix 3)
- Add questionsBadge count query to curator layout for admin branch (Fix 4)
- Fire-and-forget email sends with void Promise.all (Fix 5)
- Wrap req.json() calls in try/catch returning 400 on parse failure (Fix 6)

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/app/api/questions/[id]/messages/route.ts

@@ -10,6 +10,13 @@ interface FileAttachment {
   size: number;
 }
 
+function buildS3Prefix(): string {
+  const endpoint = process.env.S3_ENDPOINT ?? "";
+  const bucket = process.env.S3_BUCKET ?? "";
+  // e.g. https://fsn1.your-objectstorage.com/lms-uploads/
+  return `${endpoint}/${bucket}/`;
+}
+
 export async function POST(
   req: NextRequest,
   { params }: { params: Promise<{ id: string }> }
@@ -33,23 +40,32 @@ export async function POST(
     return NextResponse.json({ error: "Question is closed" }, { status: 409 });
   }
 
-  const body = await req.json();
+  let body: unknown;
+  try {
+    body = await req.json();
+  } catch {
+    return NextResponse.json({ error: "Invalid JSON" }, { status: 400 });
+  }
   const { text, files } = body as { text: string; files?: FileAttachment[] };
 
   if (!text?.trim()) {
     return NextResponse.json({ error: "text is required" }, { status: 400 });
   }
 
+  const s3Prefix = buildS3Prefix();
   const safeFiles = files
     ?.filter(
       (f) =>
         typeof f.name === "string" &&
         typeof f.url === "string" &&
+        f.url.startsWith("https://") &&
+        f.url.startsWith(s3Prefix) &&
         typeof f.size === "number"
     )
     .map((f) => ({ name: f.name.slice(0, 255), url: f.url, size: Math.max(0, f.size) }));
 
-  const message = await prisma.studentQuestionMessage.create({
+  const [msg] = await prisma.$transaction([
+    prisma.studentQuestionMessage.create({
       data: {
         questionId: id,
         authorId: session.user.id,
@@ -57,17 +73,16 @@ export async function POST(
         files: safeFiles?.length ? (safeFiles as object[]) : undefined,
       },
       include: { author: { select: { id: true, name: true, role: true } } },
-  });
+    }),
-
+    prisma.studentQuestion.update({
-  // Touch question.updatedAt
-  await prisma.studentQuestion.update({
       where: { id },
       data: { updatedAt: new Date() },
-  });
+    }),
+  ]);
 
-  // Send notifications
+  // Send notifications (fire-and-forget, outside transaction)
   if (isStaff) {
-    await sendQuestionReplyEmail(
+    void sendQuestionReplyEmail(
       question.user.email,
       question.user.name,
       question.title,
@@ -78,12 +93,12 @@ export async function POST(
       where: { role: { in: ["admin", "curator"] } },
       select: { email: true, name: true },
     });
-    await Promise.all(
+    void Promise.all(
       staff.map((s) =>
         sendQuestionFollowUpEmail(s.email, s.name, session.user.name, question.title)
       )
     );
   }
 
-  return NextResponse.json(message, { status: 201 });
+  return NextResponse.json(msg, { status: 201 });
 }

src/app/api/questions/route.ts

@@ -53,7 +53,12 @@ export async function POST(req: NextRequest) {
     return NextResponse.json({ error: "Forbidden" }, { status: 403 });
   }
 
-  const body = await req.json();
+  let body: unknown;
+  try {
+    body = await req.json();
+  } catch {
+    return NextResponse.json({ error: "Invalid JSON" }, { status: 400 });
+  }
   const { title, text, courseId } = body as {
     title: string;
     text: string;
@@ -82,7 +87,7 @@ export async function POST(req: NextRequest) {
     where: { role: { in: ["admin", "curator"] } },
     select: { email: true, name: true },
   });
-  await Promise.all(
+  void Promise.all(
     staff.map((s) =>
       sendQuestionCreatedEmail(s.email, s.name, session.user.name, title.trim())
     )

src/app/curator/layout.tsx

@@ -5,6 +5,7 @@ import Link from "next/link";
 import { LogoutButton } from "@/components/layout/logout-button";
 import { AdminShell } from "@/components/admin/admin-shell";
 import { getSetting } from "@/lib/settings";
+import { prisma } from "@/lib/prisma";
 
 export default async function CuratorLayout({ children }: { children: React.ReactNode }) {
   const session = await auth.api.getSession({ headers: await headers() });
@@ -19,7 +20,17 @@ export default async function CuratorLayout({ children }: { children: React.Reac
 
   // Admin uses the admin shell with sidebar
   if (session.user.role === "admin") {
-    return <AdminShell userName={session.user.name}>{children}</AdminShell>;
+    const questionsBadge = await prisma.studentQuestion.count({
+      where: {
+        messages: {
+          some: {
+            isRead: false,
+            author: { role: "student" },
+          },
+        },
+      },
+    });
+    return <AdminShell userName={session.user.name} questionsBadge={questionsBadge}>{children}</AdminShell>;
   }
 
   return (

src/components/questions/QuestionSplitView.tsx

@@ -295,7 +295,7 @@ export function QuestionSplitView({ currentUserId }: { currentUserId: string })
                         {msg.files.map((f) => (
                           <a
                             key={f.url}
-                            href={f.url}
+                            href={f.url.startsWith("https://") ? f.url : "#"}
                             target="_blank"
                             rel="noopener noreferrer"
                             className="flex items-center gap-1.5 text-xs px-2 py-1 rounded-sm"

src/components/questions/QuestionThread.tsx

@@ -146,7 +146,7 @@ export function QuestionThread({
                   {msg.files.map((f, i) => (
                     <a
                       key={i}
-                      href={f.url}
+                      href={f.url.startsWith("https://") ? f.url : "#"}
                       target="_blank"
                       rel="noreferrer"
                       className="flex items-center gap-1.5 text-xs px-2 py-1 rounded-sm"