NoSQL injection is a type of web application security vulnerability that occurs when user-supplied input is not properly sanitized before being used in a NoSQL query. This can allow an attacker to inject malicious code into the query, potentially gaining access to sensitive data or compromising the integrity of the database.

Here are some examples of NoSQL injection:

1. An attacker could supply a string as input that contains a MongoDB query. For example, the user might enter a search query for a username that includes a malicious command to delete all entries in the database:

username=admin'; db.users.remove({}); //

2. An attacker could also use NoSQL injection to bypass authentication by supplying a string that evaluates to true when used in a NoSQL query. For example, the attacker could enter the following as a username:

username=admin' OR 1=1; //

3. Another common technique is to use NoSQL injection to extract sensitive information from the database. For example, the attacker could enter a string that causes the NoSQL query to return all user records, including sensitive information such as passwords and email addresses:

username=admin' UNION SELECT * FROM users; //




4 . An attacker could use NoSQL injection to add additional conditions to a query, potentially allowing them to access data that they would not normally have access to. For example, the attacker could enter a string that causes the NoSQL query to return only those records that match a certain condition:

username=admin' AND password='12345'; //


5. An attacker could also use NoSQL injection to modify data in the database. For example, the attacker could enter a string that causes the NoSQL query to update a user's password to a value of their choosing:

username=admin'; db.users.update({}, {$set: {password: 'hacked'}}); //


6. In some cases, an attacker may use NoSQL injection to execute arbitrary code on the server. For example, the attacker could enter a string that causes the NoSQL query to execute a JavaScript function of their choosing:

username=admin'; db.eval('function() { /* malicious code here */ }'); //


It is important to note that these are just a few examples of NoSQL injection, and that attackers can use many other techniques to exploit this vulnerability. To protect against NoSQL injection, it is important to sanitize user-supplied input and properly escape any special characters before using it in a NoSQL query.