Describe how to prevent NoSQL injection attacks when using Mongoose with MongoDB, focusing on sanitizing user inputs.

NoSQL injection attacks exploit vulnerabilities in applications that use NoSQL databases like MongoDB. The core principle of preventing these attacks with Mongoose is to *avoid directly embedding user-provided data into MongoDB queries. Instead, use parameterized queries and Mongoose's built-in sanitization and validation features. 1. Parameterized Queries (Mongoose Models): The primary defense is to use Mongoose models and methods to construct queries, rather than building query strings manually. Mongoose automatically escapes and sanitizes data when you use its methods. For example, instead of `db.collection('users').find({name: req.query.name})` (which is vulnerable), use `User.find({name: req.query.name})` where `User` is a Mongoose model. Mongoose will handle the escaping and sanitization of the `req.query.name` value. 2. Input Validation: Define schemas in Mongoose that specify the data types and validation rules for each field. This ensures that only valid data is stored in the database. For example, you can specify that a field is a string, number, or email address, and you can also set minimum and maximum lengths or use regular expressions to validate the format. Example: `const userSchema = new mongoose.Schema({ email: { type: String, required: True, match: /^[^s@]+@[^s@]+.[^s@]+$/ }, age: { type: Number, min: 18, max: 120 } });` 3. Sanitization Libraries: For more complex sanitization requirements, consider using a sanitization library like `validator.js` to sanitize user inputs *beforethey are passed to Mongoose. This allows you to remove or escape potentially harmful characters or patterns. 4. Avoid `eval()` and `JavaScript` Operators: Never use `eval()` or the `$where` operator in MongoDB queries with user-provided data. These can execute arbitrary JavaScript code, making your application highly vulnerable to injection attacks. 5. Limit Query Operators: Avoid allowing users to directly specify MongoDB query operators (e.g., `$gt`, `$lt`, `$regex`). If you need to allow filtering, provide a limited and predefined set of allowed operators. By combining these techniques, you can significantly reduce the risk of NoSQL injection attacks and protect your application from malicious data manipulation.