=== How to fix it in Symfony

The following code is vulnerable to cross-site scripting because it returns an HTML response that contains user input.

If you do not intend to send HTML code to clients, the vulnerability can be fixed by specifying the type of data returned in the response.
For example, you can use the class `JsonResponse` to return JSON messages safely.

==== Non-compliant code example

[source,php,diff-id=1,diff-type=noncompliant]
----
use Symfony\Component\HttpFoundation\Response;

$response = new Response();
$response->setContent(json_encode(['data' => $input]));
----

==== Compliant solution

[source,php,diff-id=1,diff-type=compliant]
----
use Symfony\Component\HttpFoundation\JsonResponse;

$response = new JsonResponse(['data' => $input]);
----

It is also possible to set the content-type manually using the `headers` attribute.

==== Non-compliant code example

[source,php,diff-id=2,diff-type=noncompliant]
----
use Symfony\Component\HttpFoundation\Response;

$response = new Response();
$response->setContent($input);
----

==== Compliant solution

[source,php,diff-id=2,diff-type=compliant]
----
use Symfony\Component\HttpFoundation\Response;

$response = new Response();
$response->headers->set('Content-Type', 'text/plain');
$response->setContent($input);
----

=== How does this work?

If the HTTP response is HTML code, it is highly recommended to use a template engine like https://twig.symfony.com/[Twig] to generate it.
This template engine separates the view from the business logic and automatically encodes the output of variables, drastically reducing the risk of cross-site scripting vulnerabilities.

If you do not intend to send HTML code to clients, the vulnerability can be fixed by specifying the type of data returned in the response with the `content-type` HTTP header.
This header tells the browser that the response does not contain HTML code and should not be parsed and interpreted as HTML.
Thus, the response is not vulnerable to reflected cross-site scripting.

For example, setting the content-type to `text/plain` allows to safely reflect user input since browsers will not try to parse and execute the response.

=== Pitfalls

include::../../common/pitfalls/content-types.adoc[]

=== Going the extra mile

include::../../common/extra-mile/csp.adoc[]

