# CodeIgniter User Guide Version 2.1.1

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# Security Class

The Security Class contains methods that help you create a secure application, processing input data for security.

## XSS Filtering

CodeIgniter comes with a Cross Site Scripting Hack prevention filter which can either run automatically to filter all POST and COOKIE data that is encountered, or you can run it on a per item basis. By default it does not run globally since it requires a bit of processing overhead, and since you may not need it in all cases.

The XSS filter looks for commonly used techniques to trigger Javascript or other types of code that attempt to hijack cookies or do other malicious things. If anything disallowed is encountered it is rendered safe by converting the data to character entities.

Note: This function should only be used to deal with data upon submission. It's not something that should be used for general runtime processing since it requires a fair amount of processing overhead.

To filter data through the XSS filter use this function:

## $this->security->xss_clean()

Here is an usage example:

`$data = $this->security->xss_clean($data);`

If you want the filter to run automatically every time it encounters POST or COOKIE data you can enable it by opening your `application/config/config.php` file and setting this:

`$config['global_xss_filtering'] = TRUE;`

Note: If you use the form validation class, it gives you the option of XSS filtering as well.

An optional second parameter, is_image, allows this function to be used to test images for potential XSS attacks, useful for file upload security. When this second parameter is set to TRUE, instead of returning an altered string, the function returns TRUE if the image is safe, and FALSE if it contained potentially malicious information that a browser may attempt to execute.

`if ($this->security->xss_clean($file, TRUE) === FALSE)
{
// file failed the XSS test
}`

## $this->security->sanitize_filename()

When accepting filenames from user input, it is best to sanitize them to prevent directory traversal and other security related issues. To do so, use the sanitize_filename() method of the Security class. Here is an example:

`$filename = $this->security->sanitize_filename($this->input->post('filename'));`

If it is acceptable for the user input to include relative paths, e.g. `file/in/some/approved/folder.txt`, you can set the second optional parameter, `$relative_path` to TRUE.

`$filename = $this->security->sanitize_filename($this->input->post('filename'), TRUE);`

## Cross-site request forgery (CSRF)

You can enable csrf protection by opening your `application/config/config.php` file and setting this:

`$config['csrf_protection'] = TRUE;`

If you use the form helper the form_open() function will automatically insert a hidden csrf field in your forms.