GHSA-5846-7qm3-r52j

## Summary

is_url_safe can treat localhost as safe when DNS resolver 1.1.1.1 returns NXDOMAIN because dns.resolve4 yields no address and no dns.lookup fallback occurs, allowing server-side request forgery.

## POC

Example to simulate 1.1.1.1 in version before 1.5.0 of dssrf:

```js import { is_url_safe } from '../dist/helpers.js'; import dns from 'dns';

dns.setServers(['1.1.1.1']);

const TARGET = 'http://localhost/admin';

console.log(`Testing: ${TARGET}`); console.log(`Current DNS Servers: ${dns.getServers()}`);

const result = await is_url_safe(TARGET);

if (result === true) { console.log('dssrf treated localhost as SAFE because 1.1.1.1 returned NXDOMAIN.'); } else { console.log('dssrf blocked localhost.'); } ```