Open Redirect in Mongodb

Open redirect vulnerabilities in Mongodb applications typically emerge through URL handling in API endpoints that interact with database operations. When Mongodb-based applications process redirect URLs stored in database fields or construct redirect URLs using query parameters that eventually hit Mongodb queries, attackers can manipulate these flows to redirect users to malicious sites.

A common Mongodb-specific pattern occurs when applications store redirect URLs in database documents and later retrieve them for navigation. Consider a user profile document in Mongodb:

{
  _id: ObjectId("64a1b2c3d4e5f6g7h8i9j0k"),
  username: "john_doe",
  redirect_url: "https://example.com/welcome"
}

If the application retrieves this redirect_url and performs an HTTP redirect without validation, an attacker who gains write access to the database (through injection or other means) can set this field to a malicious URL:

{
  _id: ObjectId("64a1b2c3d4e5f6g7h8i9j0k"),
  username: "john_doe",
  redirect_url: "https://phishing-site.com/steal-credentials"
}

Another Mongodb-specific scenario involves aggregation pipelines that construct URLs. When using the $concat operator to build redirect URLs from database fields, improper validation can lead to open redirect:

db.users.aggregate([
  {
    $match: { _id: ObjectId(req.params.id) }
  },
  {
    $project: {
      redirect_url: {
        $concat: ["https://app.com/", "$username", "/dashboard"]
      }
    }
  }
])

If username contains malicious characters or URL fragments, the constructed URL may redirect users unexpectedly. Mongodb's flexible schema allows storing arbitrary strings in fields that might later be used for redirection, creating a unique attack surface when combined with application-level URL handling.

API endpoints that accept Mongodb document IDs and return redirect URLs based on database queries are particularly vulnerable. An endpoint like /api/v1/users/:id/redirect that queries Mongodb for a user's profile and extracts a redirect URL without validation creates an open redirect vulnerability specific to the Mongodb data model.

Detecting open redirect vulnerabilities in Mongodb applications requires examining both the database schema and application code that interfaces with Mongodb. Start by identifying fields in your Mongodb collections that store URL-like data. Use Mongodb's find command with regex patterns to locate potential redirect fields:

db.users.find({
  redirect_url: { $regex: /^https?:\/\// }
})

Scan your application code for Mongodb queries that retrieve URL fields and subsequently use them in HTTP redirects. Look for patterns where Mongodb document fields are directly passed to response redirect functions without validation. Common vulnerable patterns include:

// Vulnerable: direct database field to redirect
const user = await db.users.findOne({ _id: userId });
res.redirect(user.redirect_url); // No validation!

middleBrick's API security scanner can detect these vulnerabilities by analyzing the runtime behavior of your endpoints. When scanning a Mongodb-backed API, middleBrick tests for open redirect by injecting malicious URLs into parameters that might flow through Mongodb queries and eventually trigger redirects. The scanner's black-box approach means it doesn't need access to your database or source code—it simply submits test requests and observes the responses.

For comprehensive detection, examine your Mongodb aggregation pipelines for URL construction operations. The $concat, $replaceRoot, and other string manipulation operators can create redirect URLs from database fields. middleBrick's scanning engine tests these code paths by observing the API's response to crafted inputs, identifying when Mongodb-processed data leads to unauthorized redirects.

middleBrick's LLM security features also help detect open redirect vulnerabilities in AI-powered applications that use Mongodb. If your application uses LLM APIs and stores conversation context or user inputs in Mongodb, middleBrick can identify when these stored values might be used to construct malicious redirects or when prompt injection attacks could manipulate Mongodb-stored data to create open redirect scenarios.

Remediating open redirect vulnerabilities in Mongodb applications requires a defense-in-depth approach that validates URLs both at the database level and in application code. Start by implementing a whitelist of allowed redirect domains in your Mongodb schema using JSON Schema validation:

db.createCollection('users', {
  validator: {
    $jsonSchema: {
      bsonType: 'object',
      required: ['username'],
      properties: {
        username: {
          bsonType: 'string',
          description: 'must be a string and is required'
        },
        redirect_url: {
          bsonType: 'string',
          pattern: '^https?:\/\/(www\.)?example\.com\/.*$',
          description: 'must be a valid redirect URL within allowed domains'
        }
      }
    }
  }
});

This schema validation prevents storing malicious URLs directly in Mongodb documents. For existing data, use Mongodb's update operations to sanitize redirect URLs:

db.users.updateMany(
  { redirect_url: { $exists: true } },
  {
    $set: {
      redirect_url: {
        $cond: [
          { $regexMatch: { input: "$redirect_url", regex: /^https?:\/\/(www\.)?example\.com\/.*$/ } },
          "$redirect_url",
          "https://example.com/default"
        ]
      }
    }
  }
);

In application code, implement robust URL validation before performing redirects. Use Node.js libraries like valid-url or custom validation functions:

const validUrl = require('valid-url');

async function safeRedirect(req, res) {
  const userId = req.params.id;
  const user = await db.users.findOne({ _id: ObjectId(userId) });
  
  if (!user || !user.redirect_url) {
    return res.status(404).send('User not found');
  }
  
  // Validate URL against whitelist
  const allowedDomains = ['https://example.com', 'https://app.com'];
  const isValid = allowedDomains.some(domain => 
    user.redirect_url.startsWith(domain)
  );
  
  if (!isValid) {
    console.warn(`Blocked redirect attempt to: ${user.redirect_url}`);
    return res.status(400).send('Invalid redirect URL');
  }
  
  res.redirect(user.redirect_url);
}

For aggregation pipelines that construct URLs, validate the final output before using it for redirects. Use Mongodb's $cond operator to provide safe defaults:

db.users.aggregate([
  {
    $match: { _id: ObjectId(req.params.id) }
  },
  {
    $project: {
      safe_redirect: {
        $cond: [
          { 
            $and: [
              { $eq: [ "$username", "admin" ] },
              { $regexMatch: { input: "$username", regex: /^[a-zA-Z0-9_-]+$/ } }
            ]
          },
          {
            $concat: ["https://app.com/", "$username", "/dashboard"]
          },
          "https://app.com/default"
        ]
      }
    }
  }
])

middleBrick's GitHub Action can help maintain these remediations by scanning your Mongodb-backed APIs in CI/CD pipelines. Configure it to fail builds if open redirect vulnerabilities are detected, ensuring that security fixes aren't accidentally removed during development.