Sanitize your express payload to prevent MongoDB operator injection.
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Latest commit ae45543 Jan 12, 2017

Express Mongoose Sanitize

Express 4.x middleware which sanitizes user-supplied data to prevent MongoDB Operator Injection.

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npm install express-mongo-sanitize


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

var express = require('express'),
    bodyParser = require('body-parser'),
    mongoSanitize = require('express-mongo-sanitize');

var app = express();

app.use(bodyParser.urlencoded({extended: true}));

// To remove data, use:

// Or, to replace prohibited characters with _, use:
  replaceWith: '_'

You can also bypass the middleware and use the module directly:

var mongoSanitize = require('express-mongo-sanitize');

var payload = {...};

// Remove any keys containing prohibited characters

// Replace any prohibited characters in keys
mongoSanitize.sanitize(payload, {
  replaceWith: '_'

// Check if the payload has keys with prohibited characters
var hasProhibited = mongoSanitize.has(payload);


This module searches for any keys in objects that begin with a $ sign or contain a ., from req.body, req.query or req.params. It can then either:

  • completely remove these keys and associated data from the object, or
  • replace the prohibited characters with another allowed character.

The behaviour is governed by the passed option, replaceWith. Set this option to have the sanitizer replace the prohibited characters with the character passed in.

See the spec file for more examples.


Object keys starting with a $ or containing a . are reserved for use by MongoDB as operators. Without this sanitization, malicious users could send an object containing a $ operator, or including a ., which could change the context of a database operation. Most notorious is the $where operator, which can execute arbitrary JavaScript on the database.

The best way to prevent this is to sanitize the received data, and remove any offending keys, or replace the characters with a 'safe' one.


Inspired by mongo-sanitize.