AIKIDO-2026-179881

TL;DR

JsonSchemaCoercer in the smart coercion plugin coerces request input before schema validation and mishandles object keys that name Object.prototype members. An attacker who can reach a procedure whose input schema contains an object can send keys such as __proto__ or constructor to replace the prototype of the coerced input object or make inherited members pass the coercer's satisfaction check. The effect is scoped to the single coerced value returned for that request rather than the global Object.prototype, but a handler that reads inherited properties can act on data the client never legitimately supplied. The fix collects coerced properties into a null-prototype object and restricts sub-schema lookups to own properties via Object.hasOwn.