Express XSS Sanitizer

Express 4.x and 5.x middleware which sanitizes user input data (in req.body, req.query, req.headers and req.params) to prevent Cross Site Scripting (XSS) attack.

Installation

$ npm install express-xss-sanitizer

Usage

Add as a piece of express middleware, before defining your routes.

const express = require('express');
const bodyParser = require('body-parser');
const { xss } = require('express-xss-sanitizer');

const app = express();

app.use(bodyParser.json({limit:'1kb'}));
app.use(bodyParser.urlencoded({extended: true, limit:'1kb'}));
app.use(xss());

You can add options to control max number of recursion at sanitization to prevent DOS attacks.

const options = {
   maxDepth: 50, // default 100
}

app.use(xss(options));

You can add options to specify allowed keys or allowed attributes to be skipped at sanitization

const options = {
   allowedKeys: ['name'],
   allowedAttributes: {
         input: ['value'],
   },
}

app.use(xss(options));

You can add options to specify allowed tags to sanitize it and remove other tags

const options = {
   allowedTags: ['h1']
}

app.use(xss(options));

Add as a piece of express middleware, before single route.

const express = require('express');
const bodyParser = require('body-parser');
const { xss } = require('express-xss-sanitizer');

const app = express();

app.use(bodyParser.json({limit:'1kb'}));
app.use(bodyParser.urlencoded({extended: true, limit:'1kb'}));
app.post("/body", xss(), function (req, res) {
      // your code
});

app.post("/test", function (req, res) {
      // your code
});

Note: if you adding xxs() as application level middleware, the xxs() will sanitize req.body, req.headers and req.query only and for req.params you must add xxs() as route level middleware like below example.

const express = require('express');
const bodyParser = require('body-parser');
const { xss } = require('express-xss-sanitizer');

const app = express();

app.use(bodyParser.json({limit:'1kb'}));
app.use(bodyParser.urlencoded({extended: true, limit:'1kb'}));
app.post("/params/:val", xss(), function (req, res) {
      // your code
});

You also can sanitize your data (object, array, string,etc) on the fly.

const { sanitize } = require('express-xss-sanitizer');

// ...
      data = sanitize(data)
// or
      data = sanitize(data, {allowedKeys: ['name']})
// ...

For other frameworks

• koa-xss-sanitizer

Tests

To run the test suite, first install the dependencies, then run npm test:

$ npm install
$ npm test

Security

Reporting Vulnerabilities

Please report security issues to [email protected]

Security Updates

• v2.0.1: Fixed unbounded recursion depth vulnerability (CVE-2025-59364)

Support

Feel free to open issues on github.