diff --git a/darkbazaar/src/main.py b/darkbazaar/src/main.py
index 1053a4b..412155b 100755
--- a/darkbazaar/src/main.py
+++ b/darkbazaar/src/main.py
@@ -106,6 +106,12 @@ async def register_new_user(
     role: str = Form("seeker"),
     db: AsyncSession = Depends(get_db)
 ):
+    # SECURITY FIX: Detect HTTP Parameter Pollution
+    # Check if username, password, or role appears multiple times in form data
+    form_data = await request.form()
+    if len(form_data.getlist('username')) > 1 or len(form_data.getlist('password')) > 1 or len(form_data.getlist('role')) > 1:
+        return templates.TemplateResponse("register.html", {"request": request, "error": "Invalid request"})
+    
     user_create = UserCreate(username=username, password=password, role=role)
     new_user = await create_user(db, user_create)
     if not new_user:
@@ -120,6 +126,12 @@ async def login_user(
     password: str = Form(...),
     db: AsyncSession = Depends(get_db)
 ):
+    # SECURITY FIX: Detect HTTP Parameter Pollution
+    # Check if username or password appears multiple times in form data
+    form_data = await request.form()
+    if len(form_data.getlist('username')) > 1 or len(form_data.getlist('password')) > 1:
+        return templates.TemplateResponse("login.html", {"request": request, "error": "Invalid request"})
+    
     user = await authenticate_user(db, username, password)
     if not user:
         return templates.TemplateResponse("login.html", {"request": request, "error": "User with this credentials doesn't exist"})
@@ -258,7 +270,9 @@ async def accept_ghostlink_request_endpoint(
     if not current_user.finder_insight_requests_as_ghostlink:
         return render_profile_template(request=request, user=current_user, error="Access denied: only \'ghostlink\' role can accept request.")
     
-    result = await accept_finder_insight_request(db, current_user, finder_username, username)
+    # SECURITY FIX: Ignore username parameter to prevent IDOR
+    # Only allow ghostlink to accept their own requests
+    result = await accept_finder_insight_request(db, current_user, finder_username, None)
     if isinstance(result, str):
         ghostlink_requests = await get_all_ghostlink_requests(db, current_user.username)
         return render_relationships_template(request=request, user=current_user, ghostlink_requests=ghostlink_requests, error=result)
@@ -303,7 +317,9 @@ async def get_fulfilled_descriptions(
     if current_user.role != 'finder':
         raise HTTPException(status_code=status.HTTP_403_FORBIDDEN, detail="Access denied: only 'finder' role can view fulfilled descriptions.")
 
-    fulfilled_requests_orm = await get_all_fulfilled_seeker_requests(db, username)
+    # SECURITY FIX: Only allow finder to query their own data
+    # Ignore the username parameter and use authenticated user's username
+    fulfilled_requests_orm = await get_all_fulfilled_seeker_requests(db, current_user.username)
     return [FinderItemBase.model_validate(req) for req in fulfilled_requests_orm]