GHSA-88f2-fpv8-89q2

### Summary

When Orval is configured with `output.baseUrl.getBaseUrlFromSpecification: true`, it bakes the spec's `servers[0].url` into the generated request URL as a template literal without escaping the backtick. A server URL containing a backtick closes the template literal and injects a concatenation expression evaluated when the generated URL/request function is called, executing attacker-controlled code. Verified on Orval 8.19.0 (fetch client); survives default OpenAPI validation.

### Details

```ts return `http://api.x/` + (globalThis.X = require("fs").writeFileSync("/marker","pwned")) + `/v1/u`; ```

Prerequisite: the documented `getBaseUrlFromSpecification: true` option (takes the base URL from the OpenAPI servers block). This is the same output sink as the route-path case (request-URL template literal) reached via the server `url` field. Distinct from Orval's published CVEs (CVE-2026-22785 summary/MCP, CVE-2026-23947 / CVE-2026-25141 x-enumDescriptions, CVE-2026-24132 const/mock).

### PoC

`reproduce.sh` (+ `make_spec.py`) attached: generates a fetch client with `getBaseUrlFromSpecification: true`, bundles it, calls the functions, and shows a marker written. Verified on 8.19.0.

### Impact

With that option enabled, code execution in any environment that calls a client generated from an attacker-controlled or attacker-influenced OpenAPI description.

### Suggested fix

Escape the server URL before emitting it into the URL template literal (escape backtick and `${`), or build the base URL with an encoder that treats it as data; validate the URL. [maintainer-report.txt](https://github.com/user-attachments/files/29396562/maintainer-report.txt) [make_spec.py](https://github.com/user-attachments/files/29396563/make_spec.py) [reproduce.sh](https://github.com/user-attachments/files/29396564/reproduce.sh)