## Security

Since styled-components allows you to use arbitrary input as interpolations, you must be
careful to sanitize that input. Using user input as styles can lead to any CSS being evaluated in the user's
browser that an attacker can place in your application.

This example shows how bad user input can even lead to API endpoints being called on a user's
behalf.

```tsx
// Oh no! The user has given us a bad URL!
const userInput = '/api/withdraw-funds'

const ArbitraryComponent = styled.div`
  background: url(${userInput});
  /* More styles here... */
`
```

Be very careful! This is obviously a made-up example, but CSS injection can be unobvious and
have bad repercussions. Some IE versions even execute arbitrary JavaScript within url declarations.

There is an upcoming standard to sanitize CSS from JavaScript, [`CSS.escape`](https://developer.mozilla.org/en-US/docs/Web/API/CSS/escape). It's not very well supported across browsers yet, so we recommend using the [polyfill by Mathias Bynens](https://github.com/mathiasbynens/CSS.escape) in your app.