# Source: https://docs.datadoghq.com/security/code_security/static_analysis/static_analysis_rules/typescript-express/xss-vulnerability.md

# Source: https://docs.datadoghq.com/security/code_security/static_analysis/static_analysis_rules/javascript-express/xss-vulnerability.md

---
title: Avoid sending unsanitized user input in response
description: Datadog, the leading service for cloud-scale monitoring.
breadcrumbs: >-
  Docs > Datadog Security > Code Security > Static Code Analysis (SAST) > SAST
  Rules > Avoid sending unsanitized user input in response
---

# Avoid sending unsanitized user input in response

{% callout %}
# Important note for users on the following Datadog sites: app.ddog-gov.com

{% alert level="danger" %}
This product is not supported for your selected [Datadog site](https://docs.datadoghq.com/getting_started/site). ().
{% /alert %}

{% /callout %}

## Metadata{% #metadata %}

**ID:** `javascript-express/xss-vulnerability`

**Language:** JavaScript

**Severity:** Warning

**Category:** Security

**CWE**: [79](https://cwe.mitre.org/data/definitions/79.html)

## Description{% #description %}

Returning unsanitized user input in a `send` or `write` method can increase your application's risk of cross-site scripting attacks.

#### Learn More{% #learn-more %}

- [OWASP Cross-Site Scripting (XSS) Cheatsheet](https://cheatsheetseries.owasp.org/cheatsheets/Cross_Site_Scripting_Prevention_Cheat_Sheet.html)

## Non-Compliant Code Examples{% #non-compliant-code-examples %}

```javascript
app.get("/", (req, res) => {
    res.send(req.body.foo);
    res.send({ title: "foo", message: req.body.foo });
    res.write(req.body.foo);
    res.write({ title: "foo", message: req.body.foo });
})
```

## Compliant Code Examples{% #compliant-code-examples %}

```javascript
app.get("/", (req, res) => {
    res.send("foo");
    res.send({ title: "foo", message: 'foo' });
    res.write("foo");
    res.write({ title: "foo", message: 'foo' });
})
```
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{% icon name="icon-external-link" /%}