Property-Level Schema Confinement for Preventing Mass Assignment and Excessive Property Exposure
A user updates a profile name and secretly adds an extra field like role=admin or balance=100000 in the request body, which the server blindly saves into the database record. The verifier detects unauthorized property binding on synthetic fixtures and compiles an exact field-level allowlist contract.
Broken object property level authorization combines two closely related defects: mass assignment on input, where a framework binds client-supplied JSON keys directly onto internal database models, and excessive property exposure on output, where a serializer returns sensitive internal attributes that the caller was never meant to read.
Security Officer (Plain Meaning): Halts "Persist unauthorized privilege attribute (is_admin, role, balance) into production ORM record or leak hidden fields" before socket (0 live DB damage, signed GOST receipt)
IT Auditor & SecOps (Evidence): Scope OWASP API3:2023 (BOPLA) | Wire Rule SEC-ZD-V2-02 | Formal Witness d830a519c47e2064
Technocrat, CTO & VC (Moat): Z3 Invariant (assert (and (subset (json_input_keys req) (allowed_write_... | FP = 0.0% | Contract IMMUNE-BOP-D830A519 (mcp-sentinel 1.1.2)1. In-Path Interception and Contract Synthesis Schematic for API-BOP-02
Deterministic verification flow for API-BOP-02 (OWASP API3:2023 (BOPLA), CWE-915 / CWE-213): wire filter SEC-ZD-V2-02 intercepts destructive mutations prior to socket delivery, formal witness d830a519c47e2064 proves the flaw, and compiler emits gateway rule IMMUNE-BOP-D830A519 for mcp-sentinel.
2. Zero-Damage Wire Filtering and Formal Solver Invariant for API-BOP-02
Under rule SEC-ZD-V2-02, the software wire filter confines property-binding probes to isolated synthetic records and blocks any mutation targeting real privilege flags, billing balances, or tenant ownership attributes before socket transmission.
During testbed evaluation, the verifier submits synthetic canary properties alongside permitted profile fields and compares the serialized response against a decoy handler enforcing strict data-transfer schemas. Confirmation yields formal witness d830a519c47e2064 with zero false alarms.
Class Identifier: API-BOP-02 (mass_assignment_bopla)
Taxonomy Concordance: OWASP API3:2023 (BOPLA) | CWE-915 / CWE-213
Execution Mode: Active Safe Probing (AUTO_SCAN)
Candidate Probe: PATCH /api/v1/users/me {"display_name":"Alex","is_admin":true,"account_balance":999999,"internal_tier":"enterprise_unlimited"}
Blocked Mutation: Persist unauthorized privilege attribute (is_admin, role, balance) into production ORM record or leak hidden fields
Z3 Solver Invariant: (assert (and (subset (json_input_keys req) (allowed_write_props route role)) (subset (json_output_keys resp) (allowed_read_props route role))))
Wire Sandbox Rule: SEC-ZD-V2-02
Formal Witness Hash: d830a519c47e2064
Compiled Sentinel Rule: IMMUNE-BOP-D830A519 (mcp-sentinel 1.1.2)3. Autonomous Synthesis of Gateway Contract IMMUNE-BOP-D830A519 and Streebog-256 Receipt
Witness d830a519c47e2064 compiles into contract IMMUNE-BOP-D830A519 for border enforcement. The rule enforces a strict per-role property allowlist on both incoming request bodies and outgoing response objects inside mcp-sentinel.
4. Engineering Reference Notes for API-BOP-02
Why object-level authorization checks do not stop property-level manipulation
A user is legitimately authorized to edit their own profile record at the object level, yet still lacks authority to modify internal administrative columns such as role, credit limit, or verification status within that same record.
Filtering sensitive internal attributes from serialized API responses
The outbound contract strips internal audit fields, password hashes, and unapproved schema keys from the response tree before the packet leaves the gateway.