Affected: npm: axios

## Summary

Axios’ Node.js HTTP adapter can route requests through an attacker-controlled proxy when `Object.prototype.proxy` is polluted and request configuration is materialized as a regular object before dispatch.

Recent axios releases harden merged request config by creating a null-prototype object. However, request interceptors run after that merge and may return a replacement config. A common immutable interceptor pattern such as `{...config}` or `Object.assign({}, config)` converts the hardened config back into a normal object. Axios then dispatches that object without re-hardening it, and the Node HTTP adapter reads `config.proxy` through the prototype chain.

## Impact

In a Node.js deployment using the HTTP adapter, an attacker who can trigger prototype pollution elsewhere in the process can route affected HTTP requests through an attacker-controlled proxy.

The highest confirmed impact is for plaintext HTTP requests. The proxy can observe explicit `Authorization` headers, axios-generated Basic auth from `config.auth`, request method, absolute URL, `Host`, and request body content. The proxy can also return its own response to axios for the affected request.

This does not establish browser impact. It also does not establish HTTPS header or body disclosure under normal TLS validation.

## Affected Functionality

Affected functionality is limited to axios requests that use the Node.js HTTP adapter, including default Node usage when the HTTP adapter is selected and…