Just sufficient output filtering to prevent XSS!
GoalsMore Secure. Context-dependent output filters that are developer-friendly. It is safe to apply these filters like so:
document.write("<a href=" + xssFilters.uriInUnQuotedAttr(url) + ">" + xssFilters.uriInHTMLData(url) + "</a>");
In this example, the traditional wisdom of blindly escaping some special html entity characters (& < > ' " `) would not stop XSS (e.g., when url is equal to javascript:alert(1) or onclick=alert(1)).
Faster with Just Sufficient Encoding. Encode the minimal set of characters to thwart JavaScript executions, thus preventing XSS attacks while keeping most characters intact. Compared to the traditional blindly escape filter, our filters are up to two times faster, and there is no more double-encoding problems such as '&lt;'!!
Figure 1. "Just sufficient" encoding based on the HTML5 spec.
Install the xss-filters npm, and include it as a dependency for your project.
npm install xss-filters --save
Require xss-filters, and you may use it with your favorite template engine. Or just use it directly:
Client-side (browser)var express = require('express');
var app = express();
var xssFilters = require('xss-filters');
Â
app.get('/', function(req, res){
  var firstname = req.query.firstname;Â
  res.send('<h1> Hello, ' + xssFilters.inHTMLData(firstname) + '!</h1>');
});
Â
app.listen(3000);
Simply download the latest minified version from the dist/ folder OR from the CDN. Embed it in your HTML file, and all filters are available in a global object called xssFilters.
API Documentations WARNINGS<!doctype html>
...
<script src="dist/xss-filters.min.js"></script>
<script>
var firstname = "...";Â
document.write('<h1> Hello, ' + xssFilters.inHTMLData(firstname) + '!</h1>')
</script>Â
(1) Filters MUST ONLY be applied to UTF-8-encoded documents.
(2) DON'T apply any filters inside any scriptable contexts, i.e., <script>, <style>, <object>, <embed>, and <svg> tags as well as style="" and onXXX="" (e.g., onclick) attributes. It is unsafe to permit untrusted input inside a scriptable context.
A workaround, if you need to include data for JS, is to use:
<input id="strJS" value="{{{inDoubleQuotedAttr data}}}">
and retrieve your data with document.getElementById('strJS').value.
There are five context-sensitive filters for generic input:
<div> {{{inHTMLData data}}} </div><!-- {{{inHTMLComment comment}}} --><input value=' {{{inSingleQuotedAttr value}}} '/><input value=" {{{inDoubleQuotedAttr value}}} "/><input value= {{{inUnQuotedAttr value}}} />Here we use {{{ }}} to indicate output expression to ease illustrations
Whenever possible, apply the most specific filter that describes your context and data:
Input\Context HTMLData HTMLComment SingleQuotedAttr DoubleQuotedAttr UnQuotedAttr Full URI uriInHTMLData() uriInHTMLComment() uriInSingleQuotedAttr() uriInDoubleQuotedAttr() uriInUnQuotedAttr() URI Path uriPathInHTMLData() uriPathInHTMLComment() uriPathInSingleQuotedAttr() uriPathInDoubleQuotedAttr() uriPathInUnQuotedAttr() URI Query uriQueryInHTMLData() uriQueryInHTMLComment() uriQueryInSingleQuotedAttr() uriQueryInDoubleQuotedAttr() uriQueryInUnQuotedAttr() URI Component uriComponentInHTMLData() uriComponentInHTMLComment() uriComponentInSingleQuotedAttr() uriComponentInDoubleQuotedAttr() uriComponentInUnQuotedAttr() URI Fragment uriFragmentInHTMLData() uriFragmentInHTMLComment() uriFragmentInSingleQuotedAttr() uriFragmentInDoubleQuotedAttr() uriFragmentInUnQuotedAttr()Check out the documentations for more details.
ContributingTo contribute, make changes in src/ and tests/, and then do:
Licensenpm test             Â
npm run-script build Â
npm run-script docs  Â
This software is free to use under the Yahoo BSD license. See the LICENSE file for license text and copyright information.
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