Affected: npm: webpack

### Summary When `experiments.buildHttp` is enabled, webpack’s HTTP(S) resolver (`HttpUriPlugin`) can be bypassed to fetch resources from **hosts outside `allowedUris`** by using crafted URLs that include **userinfo** (`username:password@host`). If `allowedUris` enforcement relies on a **raw string prefix check** (e.g., `uri.startsWith(allowed)`), a URL that *looks* allow-listed can pass validation while the actual network request is sent to a different authority/host after URL parsing. This is a **policy/allow-list bypass** that enables **build-time SSRF behavior** (outbound requests from the build machine to internal-only endpoints, depending on network access) and **untrusted content inclusion** (the fetched response is treated as module source and bundled). In my reproduction, the internal response was also persisted in the buildHttp cache.

Reproduced on: - webpack version: **5.104.0** - Node version: **v18.19.1**

### Details **Root cause (high level):** `allowedUris` validation can be performed on the raw URI string, while the actual request destination is determined later by parsing the URL (e.g., `new URL(uri)`), which interprets the **authority** as the part after `@`.

Example crafted URL: - `http://127.0.0.1:9000@127.0.0.1:9100/secret.js`

If the allow-list is `["http://127.0.0.1:9000"]`, then: - Raw string check: `crafted.startsWith("http://127.0.0.1:9000")` → **true** - URL parsing (WHAT `new URL()` will contact): `origin` → `http://127.0.0.1:9100` (hos…