Admin Request Sanitization

How data is sanitized on the admin side

The Admin Sanitization features use a number of sanitization groups. Each group performs a sanitization on specific GET/POST parameters. For GET/POST parameters that are not already sanitized within these groups we then run a default sanitization (i.e.: simply running htmlspecialchars() on it).

Why Sanitize?

Historically, weaker sanitization was used for two reasons:

Firstly, Admin allows lots of parameters to include what would be considered dangerous characters. e.g. product descriptions allow script tags, and other inputs allow some html, such as product names.

Secondly, core code uses CSRF tokens for all form interactions. The use of these tokens mitigates against any exploiting of XSS, unless an admin session is already available.

However, reports such as made us reconsider. While we still contend that the CSRF protection mitigates these supposed XSS vulnerabilities, there are three good reasons to address them with extra sanitization:

  1. We cannot guarantee that 3rd party plugins use the CSRF token system (although there are some safeties to ensure they do).

  2. PCI scanning software may detect XSS vulnerabilities, even given the CSRF mitigation. (particularly where the scanner bypasses/grants admin logins)

  3. Good security practice.

TEMPORARILY Disabling Strict Sanitization

If you find that some of your pre-v1.5.5 admin plugins are no longer working properly then you should look first to see if new versions of those plugins are available, i.e.: that support the sanitization methods implemented since v1.5.5.

If new versions are not available, or you need to keep your current admin working while you update, then you can disable the strict(default) sanitization by doing the following:

Create a new disable_strict_sanitize.php file in your /admin/includes/extra_configures/ directory. The contents of this file should be

  define('DO_STRICT_SANITIZATION', false);

We encourage you to NOT do that unless truly necessary, and even then only as a temporary measure until your affected plugins have written their own custom sanitizers as described later in this document.


The AdminSanitizer class can log the actions it takes, and this may be helpful in debugging problems with plugins.

Logging is enabled/disabled using the DO_DEBUG_SANITIZATION define.

To enable logging create a new file in /admin/includes/extra_configures/ that contains

  define('DO_DEBUG_SANITIZATION', true);

For Developers. How to use the sanitization in plugins.

If you are a developer who wants to update your current code, or you are developing a new plugin, the following are some tips to keep your plugin compatible with core functionality.

Parameter Naming

GET/POST parameters will be sanitized based on their parameter name and the sanitization group assigned to them. Therefore, if you are writing a plugin and use a parameter name that already exists in Zen Cart that parameter will be sanitized according to the group it is already assigned to in core code.

For example, the action parameter is assigned to the SIMPLE_ALPHANUM_PLUS group, and the sanitization for that group will always be applied to it.

There will be occasions where a plugin uses a parameter name that is already added to a sanitization group, and rewriting plugin code may be onerous. For these cases it is possible to override sanitization on a per page basis.

Adding Parameters/Groups

If a plugin needs to define its own sanitization or override the sanitization for an already defined parameter, it should create a php file in /admin/includes/extra_datafiles/

An example of the contents might be

$sanitizer = AdminRequestSanitizer::getInstance();
$group = array(
    'id' => array('sanitizerType' => 'CONVERT_INT', 'method' => 'both', 'pages' => array('edit_orders'), 'params' => array()),


$sanitizer = AdminRequestSanitizer::getInstance();
$group = array(
  'col_html_text' => array('sanitizerType' => 'PRODUCT_DESC_REGEX', 'method' => 'post'),

The structure of the defining array is:

  1. sanitizerType = The name of a sanitizer group (see the group names below)
  2. method = get|post|both
  3. pages = (optional) an array of pages which this sanitizer rule will be applied to; (if not supplied, will apply to all pages)
  4. params = (optional) this is used only for the MULTI_DIMENSIONAL sanitizer, which is explained below.

Here’s a specific example from the News Box Manager plugin. The file admin/includes/extra_datafiles/news_box_manager_sanitization.php sanitizes the fields news_title and news_content when they are updated:

if (class_exists('AdminRequestSanitizer') && method_exists('AdminRequestSanitizer', 'getInstance')) {
    $news_mgr_sanitizer = AdminRequestSanitizer::getInstance();
    $news_mgr_sanitizer->addSimpleSanitization('PRODUCT_DESC_REGEX', array('news_title', 'news_content'));

The pages parameter is not specified here because this particular plugin is designed for easy extension, so that pages can be added simply by copying a single file (and requiring someone to modify this file as well to add the new page would be contrary to that intention.)

General Sanitization Groups

Zen Cart defines the following default case-insensitive sanitizers:


    GET and POST Values

    Uses [^\/ 0-9a-zA-Z_:@.-] regex


    GET and POST values

    converts value to Integer


    POST values only

    uses [^0-9a-z.!@#$%^&()_-~`+^ \\] regex


    GET and POST values

    Uses [^a-z0-9_-] regex


    GET and POST values

    Uses (<\/?scri|on(load|mouse|error|read|key)(up|down)? ?=|[^(class|style)] ?= ?(\(|")|<!) regex


    POST Values only (Deep)

    Uses htmlspecialchars($_POST[$parameterName][$pKey], ENT_COMPAT, $this->charset, false)


    GET and POST values

    Uses filter_var($_POST[$key], FILTER_SANITIZE_EMAIL)


    POST values only

    Uses htmlspecialchars($_POST[$parameterName], ENT_COMPAT, $this->charset, true)


    POST values only (Deep)

    Uses ([^0-9a-z'.!@#$%&()_-~/;:=?[]]|[><]) regex


    POST Values only (Deep)

    Uses (load=|= ?\(|<![^-]) regex


    POST Values only

    Uses [^a-z0-9_,\.\-] regex


    POST Values only

    Uses [^0-9,\.\-\+] regex


    POST Values only (Deep)

    Uses (<\/?scri|on(load|mouse|error|read|key)(up|down)? ?=|[^(class|style)] ?= ?(\(|")|<!) regex


    GET/POST Values

    Skips sanitization for the relevant parameter.


    Any parameters not previously sanitized will be sanitized with this method.


    All POST and GET “keys” containing any < or > symbols in the key will be unset()


The MULTI_DIMENSIONAL sanitizer is special in that it defines sanitization for an array of parameters, rather than one parameter as other sanitizers do.

For example, if you post the following array

[update_products] => Array
        [13] => Array
                [qty] => 1
                [name] => Microsoft IntelliMouse Explorer
                [onetime_charges] => 0.0000
                [attr] => Array
                        [3] => Array
                                [value] => 11
                                [type] => 0


                [model] => MSIMEXP
                [tax] => 0
                [final_price] => 70.95  

normal sanitizers would only address the outer update_products parameter, while what you really want to do is define parameters for qty name onetime_charges etc, and you also want to sanitize the attr sub array recursively.

to address this, you can define a MULTI_DIMENSIONAL sanitizer like this:-

$sanitizer = AdminRequestSanitizer::getInstance();
$group = array(
    'update_products' => array(
        'sanitizerType' => 'MULTI_DIMENSIONAL',
        'method' => 'post',
        'pages' => array('edit_orders'),
        'params' => array(
            'update_products' => array('sanitizerType' => 'CONVERT_INT'),
            'qty' => array('sanitizerType' => 'CONVERT_INT'),
            'name' => array('sanitizerType' => 'WORDS_AND_SYMBOLS_REGEX'),
            'onetime_charges' => array('sanitizerType' => 'CURRENCY_VALUE_REGEX'),
            'attr' => array(
                'sanitizerType' => 'MULTI_DIMENSIONAL',
                'params' => array(
                    'attr' => array('sanitizerType' => 'CONVERT_INT'),
                    'value' => array('sanitizerType' => 'CONVERT_INT'),
                    'type' => array('sanitizerType' => 'CONVERT_INT')
            'model' => array('sanitizerType' => 'WORDS_AND_SYMBOLS_REGEX'),
            'tax' => array('sanitizerType' => 'WORDS_AND_SYMBOLS_REGEX'),
            'final_price' => array('sanitizerType' => 'WORDS_AND_SYMBOLS_REGEX'),

Note that sanitizers for sub parameters are defined in the params array and that you can recursively define deeper arrays with a further MULTI_DIMENSIONAL sanitizer array.

Custom Sanitizers


Still have questions? Use the Search box in the upper right, or try the full list of FAQs. If you can't find it there, head over to the Zen Cart support forum and ask there in the appropriate subforum. In your post, please include your Zen Cart and PHP versions, and a link to your site.

Is there an error or omission on this page? Please post to General Questions on the support forum. Or, if you'd like to open a pull request, just review the guidelines and get started. You can even PR right here.
Last modified January 12, 2024 by Chris Brown (3df8af7).