Web application vulnerabilities refer to weaknesses or flaws in web-based applications that can be exploited by attackers to gain unauthorized access, steal data, or perform other malicious activities. These vulnerabilities can exist at various levels of the web application stack, including the front-end user interface, back-end server-side logic, and the communication protocols used between them.
As a result, malicious actors are continuously evolving their attack methodologies and techniques to exploit vulnerabilities in web applications. These attacks can lead to unauthorized access, data theft, or other malicious activities, causing significant damage to businesses and individuals alike. In response, web application developers and security professionals must remain vigilant and adopt proactive security measures to stay ahead of these evolving appsec threats. This requires a comprehensive understanding of the latest attack methodologies and techniques, along with regular security testing, tools and updates to keep web applications secure against these ever-evolving threats.
OWASP believes that web application vulnerabilities are a critical threat to the security of software systems and must be addressed proactively to reduce the risk of attacks.
OWASP maintains a Top 10 list of the most critical web application security risks, which is updated regularly to reflect the latest attack methodologies and techniques. This list is widely used by developers, security professionals, and organizations to prioritize their security efforts and ensure that their web applications are protected against the most common and dangerous vulnerabilities.
Top 10 Web Application Security Vulnerabilities
- SQL Injection
- Broken Access Control
- Cross-Site Scripting (XSS)
- Cross-Site Request Forgery (CSRF)
SQL Injection
SQL injection is a type of web application vulnerability that allows an attacker to inject malicious SQL code into a web application’s input fields or parameters. This can allow the attacker to execute unauthorized SQL commands against the application’s database, potentially gaining access to sensitive information or taking control of the application.
The vulnerability arises from the failure of the web application to properly validate or sanitize user input, allowing attackers to insert malicious SQL statements into the application’s queries. SQL injection attacks can be carried out through various means, such as input fields, query parameters, or even HTTP headers.
How does an SQL injection attack work to exploit web application vulnerability?
SQL attack example
SQL injection attacks exploit web application vulnerabilities by injecting malicious SQL code into an application’s input fields or parameters. The attack works by taking advantage of the failure of the web application to properly validate or sanitize user input, allowing attackers to insert malicious SQL statements into the application’s queries. The following steps describe how an SQL injection attack works:
Identify Numeric Parameters in a database
The attacker identifies an input field or parameter in a vulnerable web application that can be manipulated to inject SQL code. One common technique used by SQL injection attacks to identify numeric parameters is to inject an input value that is not a number, such as a string or a special character. If the application does not properly validate the input and converts it to a number before using it in a database query, it can result in a SQL error or unexpected behavior that can be observed by the attacker.
For example, an attacker could enter the following code into an input field:' or 1=1 or 'a'='b
If the application does not properly validate the input, this code could be used to inject a condition into a SQL query, such as:SELECT * FROM users WHERE id=' ' or 1=1 or 'a'='b'
This query would return all rows in the users table, regardless of the input parameter value.
Another technique used by SQL injection attacks to identify numeric parameters is to perform a “blind” SQL injection attack, where the attacker cannot directly observe the output of the SQL query. In this case, the attacker may use time delays or error messages to indirectly infer the data type and structure of the database.
For example, an attacker could enter the following code into an input field:' or sleep(5) --
If the application is vulnerable to SQL injection, this code could be used to inject a sleep command into the SQL query, causing a delay of 5 seconds before the response is returned. If the delay occurs, the attacker can infer that the input parameter is being treated as a string, since a numeric parameter would be immediately converted to a number and not cause a delay.
Execute malicious SQL statements
The attacker then inserts malicious SQL statements into the input field, such as adding a statement that deletes or modifies data from the database. When a user enters data into an input field, such as a login form or search box, the application takes the input and uses it to construct a SQL query that interacts with a database. If the input is not properly validated or sanitized, an attacker can inject additional SQL code into the query by including it as part of the input.
For example, consider a login form that accepts a username and password. A simple SQL query might look like this:SELECT * FROM users WHERE username='username' AND password='password'
An attacker could attempt to inject additional SQL code by entering the following text into the username field:' OR 1=1 --
This would result in the following SQL query:SELECT * FROM users WHERE username='' OR 1=1 --' AND password='password'
The -- at the end of the injected SQL code is used to comment out the rest of the legitimate SQL code, preventing any errors from occurring. The injection causes the query to return all records in the users table, regardless of the password entered.
Unsanitized input and parametrized queries
When the application receives the input, it does not properly validate or sanitize the input, allowing the malicious SQL code to be executed.
SQLi exploits vulnerability
The attacker can then exploit the vulnerability to gain unauthorized access to sensitive data or take control of the application.
For example, an attacker could enter the following code into a login form:
Username: admin’; DROP TABLE users;–
This input would be passed to the database as part of a SQL statement, causing the entire “users” table to be deleted from the database. The double hyphen “–” is used to comment out the rest of the legitimate SQL code, preventing any errors from occurring.
