include::../description.adoc[]

include::../ask-yourself.adoc[]

include::../recommended.adoc[]

== Sensitive Code Example

In Express.js application the code is sensitive if the https://www.npmjs.com/package/dns-prefetch-control[dns-prefetch-control] middleware is disabled or used without the recommended value:

----
const express = require('express');
const helmet = require('helmet');

let app = express();

app.use(
  helmet.dnsPrefetchControl({
    allow: true // Sensitive: allowing DNS prefetching is security-sensitive
  })
);
----

== Compliant Solution

In Express.js application the https://www.npmjs.com/package/dns-prefetch-control[dns-prefetch-control] or https://www.npmjs.com/package/helmet[helmet] middleware is the standard way to implement  ``++X-DNS-Prefetch-Control++`` header:

[source,javascript]
----
const express = require('express');
const helmet = require('helmet');

let app = express();

app.use(
  helmet.dnsPrefetchControl({
    allow: false // Compliant
  })
);
----

include::../see.adoc[]
ifdef::env-github,rspecator-view[]

'''
== Implementation Specification
(visible only on this page)

include::../message.adoc[]

endif::env-github,rspecator-view[]
