Hey API is an ecosystem for turning API specifications into production-ready code. Prior to 0.97.3, dist/clients/core/params.ts ships a runtime template copied into generated SDKs as params.gen.ts, and buildClientParams writes unknown slot-prefixed keys such as $body_, $headers_, $path_, and $query_ directly to the corresponding slot, allowing $query___proto__ alongside a legitimate q field to set params.query through params["query"]["proto"] = value, call Object.setPrototypeOf(params.query, value), and expose inherited attacker-controlled keys during for..in iteration. This issue is fixed in version 0.97.3.
Exploitability
AV:NAC:HPR:NUI:NScope
S:UImpact
C:LI:LA:N4.8/CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:NInput Validation