El gancho
Every PaaS leaks shape. The shapes are stable enough across customers that Shodan, Wappalyzer, and FOFA index them — `cf-ray`, `x-vercel-id`, `x-amz-cf-id`, `x-nf-request-id` are reconnaissance starting points, not bug bounty findings. Vercel deployments are particularly identifiable because Next.js's distinctive `/_next/` path structure and `__NEXT_DATA__` script tag are practically a signed signature. Most of the time this is benign — the platform identity isn't a secret. The bugs sneak in when preview URLs leak, when source maps reference internal hostnames, or when feature-flagged unreleased pages ship to production routes.
Cómo funciona
Vercel adds `x-vercel-id` (deployment + region identifier), `x-vercel-cache` (HIT / MISS / STALE), and `server: Vercel` headers to every response. Next.js apps expose `/_next/static/`, `/_next/data/[buildId]/`, and `/__nextjs_original-stack-frame` paths characteristic of the framework. The `__NEXT_DATA__` script in HTML reveals build metadata, locale info, and sometimes server-side props that should have stayed server-side. Preview deployments at `*.vercel.app` get their own URL per branch — convenient for testing, dangerous when one of those URLs gets shared externally and hits search engines or wayback archives.
El radio de impacto
Recon impact dominates — knowing the host platform helps an attacker choose tactics (which WAF, which CDN behaviors to expect). Direct impact when preview URLs leak: preview deployments often have looser access controls than production (auth disabled, debug flags on, staging API endpoints), so a leaked preview URL bypasses your production hardening. Source map references in production bundles can leak the canonical preview hostname and infrastructure details.
// what fixvibe checks
What FixVibe checks
FixVibe maps externally visible application surfaces with passive signals and safe metadata checks. Reports summarize the exposed surface and remediation priorities. For check-specific questions about exact detection heuristics, active payload details, or source-code rule patterns, contact support@fixvibe.app.
Defensas a prueba de balas
Strip identifying headers if hiding Vercel as the host matters to you — Vercel's `headers` config can override or remove `x-vercel-*` headers. Don't link preview URLs from production code, marketing pages, or shared documents — once shared they get archived. Restrict preview deployments to authenticated team members via Vercel's password protection or SSO integration. Audit your Next.js config for `experimental` flags or debug routes that shouldn't ship to production. Use the same robots.txt rules for preview as for production (or stricter — preview deployments shouldn't be indexed at all). For Vercel-hosted side projects, the platform identification is fine to leave; for enterprise deployments, consider terminating at your own CDN to mask origin.