No global state pollution

When plugins receive mutable references to shared objects — config, process.env, shared caches — any plugin can modify state that all other plugins and the host depend on. Plugin A changes config.apiUrl and Plugin B silently uses the wrong endpoint. A plugin calling require('dotenv').config() overwrites environment variables for every module in the process. CWE-454 (Unintended Variable Set from External Scope) and CWE-829 cover this class. The failure mode is load-order-dependent and nearly impossible to reproduce in isolation, making it one of the hardest bugs to diagnose in plugin ecosystems.

Freeze or deep-clone any object before passing it to plugin code. For config objects, a Proxy that throws on write gives a clear error attributing the mutation attempt to the offending plugin.

// Freeze config before passing to plugins:
const pluginConfig = Object.freeze(structuredClone(hostConfig));

// Or use a Proxy to prevent writes:
const readonlyConfig = new Proxy(config, {
  set() { throw new Error('Config is read-only for plugins'); },
  deleteProperty() { throw new Error('Config is read-only for plugins'); }
});