T09 · Insecure Skill Coding Practices
- Location
SKILL.md:272- Finding
Unauthenticated Webhook Accepts Forged Events
- Content
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Vulnerability Details
File Location:
SKILL.md, lines 272–286
Vulnerability Type: Missing webhook authentication and payload validation
Risk Level: HighVulnerable Code
python @app.route('/webhook/huoban', methods=['POST']) def huoban_webhook(): data = request.json event_type = data.get('event') # item.create / item.update / item.delete table_id = data.get('table_id') item = data.get('item') if event_type == 'item.create': # New record processing handle_new_item(table_id, item) elif event_type == 'item.update': # Updated record processing handle_update_item(table_id, item) return jsonify({"status": "ok"})Technical Analysis
The documented webhook handler treats every HTTP POST request as a trusted Huoban event. It does not verify a provider signature, shared secret, timestamp, nonce, or request origin before passing attacker-controlled
table_idanditemvalues to business-logic handlers.The endpoint also lacks strict content-type, payload-schema, field-type, and request-size validation. Consequently, anyone who can reach the route can submit fabricated events. The actual downstream effect depends on the unspecified implementations of
handle_new_itemandhandle_update_item; therefore, effects beyond unauthorized handler invocation are conditional rather than confirmed.The example also has no replay protection or idempotency control. If a legitimate request is captured or duplicated, it may be processed repeatedly.
Attack Path
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An attacker identifies a deployment based on the documented
/webhook/huobanroute. -
The attacker sends an unauthenticated POST request containing forged event data, for example:
json { "event": "item.update", "table_id": 123, "item": { "id": 456, "status": "approved" } } -
The route accepts the request without establishing that Huoban sent it.
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The attacker-contr ...[truncated 819 chars]
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- Remediation
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Remediation Suggestions
- Verify every webhook using Huoban’s documented authentication mechanism, preferably an HMAC signature over the raw request body with a secret stored in a secret manager or environment variable.
- Compare signatures using a constant-time function and reject requests with missing or invalid authentication before parsing or processing events.
- Validate signed timestamps and enforce a short acceptance window. Store event IDs or nonces to prevent replay and duplicate processing.
- Require the expected JSON content type, enforce a conservative request-size limit, and validate the payload against a strict schema. Reject missing fields, unexpected fields, unsupported event names, and invalid field types.
- Allowlist expected table identifiers and ensure each event is authorized for the intended tenant and workflow.
- Make handlers idempotent and use transactional processing where duplicate or partially completed events could cause inconsistent state.
- Return appropriate
4xxresponses for invalid requests and unsupported events instead of always returning success. - Apply rate limiting, structured security logging, and monitoring for repeated signature failures or anomalous event volume.
- Do not rely solely on source-IP allowlisting, but use it as defense in depth if Huoban publishes stable webhook source ranges.
- Add tests covering forged signatures, stale timestamps, replayed events, malformed JSON, oversized bodies, unsupported event types, and cross-tenant or unauthorized table identifiers.