CVE-2026-70610: Electron: contextBridge object copy honors prototype setters

Objects copied across the contextBridge boundary from untrusted content could carry an attacker-influenced prototype, enabling prototype-pollution-style attacks against preload code despite context isolation being enabled.

Apps are only affected if their preload code accepts object arguments from untrusted content and reads properties from them without own-property checks. Apps that only accept primitive arguments, or that validate object arguments, are not affected.