Package Exports

xss
xss/lib/default

This package does not declare an exports field, so the exports above have been automatically detected and optimized by JSPM instead. If any package subpath is missing, it is recommended to post an issue to the original package (xss) to support the "exports" field. If that is not possible, create a JSPM override to customize the exports field for this package.

Readme

Sanitize untrusted HTML (to prevent XSS) with a configuration specified by a Whitelist.

xss

NOTE: The format of custom configuration (except Whitelist) from version 0.0.X was changed a lot since version 0.1.X. To use a newer version, it's suggested to read the following guidelines carefully.

xss is a module used to filter input from users to prevent XSS attacks. (What is XSS attack?)

This module is needed for situations that allows users to input HTML for typesetting or formatting, including fourms, blogs, e-shops, etc.

The xss module controls the usage of tags and their attributes, according to the whitelist. It is also extendable with a series of APIs privided, which make it become more flexible, compares with other modules.

Project Homepage: https://github.com/leizongmin/js-xss

Features

Specifies HTML tags and their attributes allowed with whitelist
Handle any tags or attributes using custom function.

Reference

Benchmark (for references only)

the xss module: 8.2 MB/s
xss() function from module validator@0.3.7: 4.4 MB/s

For test code please refer to benchmark directory.

Unit Test

Run npm test command in the source directary.

Active Test

Run node lib/cli.js command in the source directary, them you can type HTML code in the command-line, and check the filtered output.

Usages

In Node.js

To install:

$ npm install xss

Simple usage:

var xss = require('xss');
var html = xss('<script>alert("xss");</script>');
console.log(html);

In browsers

<script src="https://raw.github.com/leizongmin/js-xss/master/build/xss.js"></script>
<script>
// apply function filterXSS in the same way
var html = filterXSS('<script>alert("xss");</scr' + 'ipt>');
alert(html);
</script>

Custom filter rules

When using the xss() function, the second parameter could be used to specify custom rules:

options = {};  // Custom rules
html = xss('<script>alert("xss");</script>', options);

To avoid passing options every time, you can also do it in a faster way by creating a FilterXSS instance:

options = {};  // Custom rules
myxss = new xss.FilterXSS(options);
// then apply myxss.process()
html = myxss.process('<script>alert("xss");</script>');

Details of parameters in options would be described below.

Whitelist

By specefing a whiteList, e.g. { 'tagName': [ 'attr-1', 'attr-2' ] }. Tags and attributes not in the whitelist would be filter out. For example:

// only tag a and its attributes href, title, target are allowed
var options = {
  whiteList: {
    a: ['href', 'title', 'target']
  }
};
// With the configuration specified above, the following HTML:
// <a href="#" onclick="hello()"><i>Hello</i></a>
// would become:
// <a href="#">Hello</a>

For the default whitelist, please refer xss.whiteList.

Customize the handler function for matched tags

By specefing the handler function with onTag:

function onTag (tag, html, options) {
  // tag is the name of current tag, e.g. 'a' for tag <a>
  // html is the HTML of this tag, e.g. '<a>' for tag <a>
  // options is some addition informations:
  //   isWhite    boolean, whether the tag is in whitelist
  //   isClosing  boolean, whether the tag is a closing tag, e.g. true for </a>
  //   position        integer, the position of the tag in output result
  //   sourcePosition  integer, the position of the tag in input HTML source
  // If a string is returned, the current tag would be replaced with the string
  // If return nothing, the default measure would be taken:
  //   If in whitelist: filter attributes using onTagAttr, as described below
  //   If not in whitelist: handle by onIgnoreTag, as described below
}

Customize the handler function for attributes of matched tags

By specefing the handler function with onTagAttr:

function onTagAttr (tag, name, value, isWhiteAttr) {
  // tag is the name of current tag, e.g. 'a' for tag <a>
  // name is the name of current attribute, e.g. 'href' for href="#"
  // isWhiteAttr whether the tag is in whitelist
  // If a string is returned, the attribute would be replaced with the string
  // If return nothing, the default measure would be taken:
  //   If in whitelist: filter the value using safeAttrValue as described below
  //   If not in whitelist: handle by onIgnoreTagAttr, as described below
}

Customize the handler function for tags not in the whitelist

By specefing the handler function with onIgnoreTag:

function onIgnoreTag (tag, html, options) {
  // Parameters are the same with onTag
  // If a string is returned, the tag would be replaced with the string
  // If return nothing, the default measure would be taken (specifies using
  // escape, as described below)
}

Customize the handler function for attributes not in the whitelist

By specefing the handler function with onIgnoreTagAttr:

function onIgnoreTagAttr (tag, name, value, isWhiteAttr) {
  // Parameters are the same with onTagAttr
  // If a string is returned, the value would be replaced with this string
  // If return nothing, then keep default (remove the attribute)
}

Customize escaping function for HTML

By specefing the handler function with escapeHtml. Following is the default function (Modification is not recommended):

function escapeHtml (html) {
  return html.replace(/</g, '&lt;').replace(/>/g, '&gt;');
}

Customize escaping function for value of attributes

By specefing the handler function with safeAttrValue:

function safeAttrValue (tag, name, value) {
  // Parameters are the same with onTagAttr (without options)
  // Return the value as a string
}

Quick Start

Filter out tags not in the whitelist

By using stripIgnoreTag parameter:

true filter out tags not in the whitelist
false: by default: escape the tag using configured escape function

Example:

If stripIgnoreTag = true is set, the following code:

code:<script>alert(/xss/);</script>

would output filtered:

code:alert(/xss/);

Filter out tags and tag bodies not in the whitelist

By using stripIgnoreTagBody parameter:

false|null|undefined by default: do nothing
'*'|true: filter out all tags not in the whitelist
['tag1', 'tag2']: filter out only specified tags not in the whitelist

Example:

If stripIgnoreTagBody = ['script'] is set, the following code:

code:<script>alert(/xss/);</script>

would output filtered:

code:

Examples

Allow attributes of whitelist tags start with `data-`

var source = '<div a="1" b="2" data-a="3" data-b="4">hello</div>';
var html = xss(source, {
  onIgnoreTagAttr: function (tag, name, value, isWhiteAttr) {
    if (name.substr(0, 5) === 'data-') {
      // escape its value using built-in escapeAttrValue function
      return name + '="' + xss.escapeAttrValue(value) + '"';
    }
  }
});

console.log('%s\nconvert to:\n%s', source, html);

Result:

<div a="1" b="2" data-a="3" data-b="4">hello</div>
convert to:
<div data-a="3" data-b="4">hello</div>

Allow tags start with `x-`

var source = '<x><x-1>he<x-2 checked></x-2>wwww</x-1><a>';
var html = xss(source, {
  onIgnoreTag: function (tag, html, options) {
    if (tag.substr(0, 2) === 'x-') {
      // do not filter its attributes
      return html;
    }
  }
});

console.log('%s\nconvert to:\n%s', source, html);

Result:

<x><x-1>he<x-2 checked></x-2>wwww</x-1><a>
convert to:
&lt;x&gt;<x-1>he<x-2 checked></x-2>wwww</x-1><a>

Parse images in HTML

var source = '<img src="img1">a<img src="img2">b<img src="img3">c<img src="img4">d';
var list = [];
var html = xss(source, {
  onTagAttr: function (tag, name, value, isWhiteAttr) {
    if (tag === 'img' && name === 'src') {
      // Use the built-in friendlyAttrValue function to escape attribute
      // values. It supports converting entity tags such as &lt; to printable
      // characters such as <
      list.push(xss.friendlyAttrValue(value));
    }
    // Return nothing, means keep the default handling measure
  }
});

console.log('image list:\n%s', list.join(', '));

Result:

image list:
img1, img2, img3, img4

Filter out HTML tags (keeps only plain text)

var source = '<strong>hello</strong><script>alert(/xss/);</script>end';
var html = xss(source, {
  whiteList:          [],        // empty, means filter out all tags
  stripIgnoreTag:     true,      // filter out all HTML not in the whilelist
  stripIgnoreTagBody: ['script'] // the script tag is a special case, we need
                                 // to filter out its content
});

console.log('text: %s', html);

Result:

text: helloend

License

The MIT License

Donate

If you love the xss module, please send me a cup of coffee :)

xss

Package Exports

Readme

Sanitize untrusted HTML (to prevent XSS) with a configuration specified by a Whitelist.

Features

Reference

Benchmark (for references only)

Unit Test

Active Test

Usages

In Node.js

In browsers

Custom filter rules

Whitelist

Customize the handler function for matched tags

Customize the handler function for attributes of matched tags

Customize the handler function for tags not in the whitelist

Customize the handler function for attributes not in the whitelist

Customize escaping function for HTML

Customize escaping function for value of attributes

Quick Start

Filter out tags not in the whitelist

Filter out tags and tag bodies not in the whitelist

Examples

Allow attributes of whitelist tags start with data-

Allow tags start with x-

Parse images in HTML

Filter out HTML tags (keeps only plain text)

License

Donate

Allow attributes of whitelist tags start with `data-`

Allow tags start with `x-`