BOLA (formerly IDOR) remains the #1 threat in the OWASP API Top 10. It occurs when an application relies on user-supplied IDs to access objects without validating ownership. In Django, this typically manifests when developers fetch an object directly from the model manager using a primary key from the URL, assuming that authentication equals authorization.

The Vulnerable Pattern

from django.http import JsonResponse
from .models import Invoice
VULNERABLE: Any authenticated user can guess an ID and access any invoice
def get_invoice(request, invoice_id):
invoice = Invoice.objects.get(id=invoice_id)
return JsonResponse({‘id’: invoice.id, ‘amount’: invoice.amount, ‘secret_note’: invoice.secret_note})

The Secure Implementation

The fix involves enforcing 'Ownership-Based Access Control' at the database layer. Instead of querying the entire table, you must scope the queryset to the current 'request.user'. By using 'get_object_or_404(Model, id=id, owner=request.user)', the ORM generates a SQL query with a WHERE clause that includes both the ID and the owner_id. If a user tries to access an ID they don't own, the database returns no record, and Django correctly triggers a 404 Not Found, preventing data leakage. For Django Rest Framework (DRF), always override 'get_queryset()' to return 'self.request.user.invoices.all()' instead of 'Invoice.objects.all()'.

from django.shortcuts import get_object_or_404
from django.http import JsonResponse
from .models import Invoice
SECURE: Query is scoped strictly to the requesting user
def get_invoice(request, invoice_id):
invoice = get_object_or_404(Invoice, id=invoice_id, owner=request.user)
return JsonResponse({‘id’: invoice.id, ‘amount’: invoice.amount, ‘secret_note’: invoice.secret_note})