SQL injection attacks occur when untrusted user data is executed as part of a SQL query due to unsecure coding practices. This article discusses the root cause and contributing factors of SQL injection and explains how DAST helps detect and prevent these vulnerabilities.
SQL injection is only possible when raw user data is directly inserted into dynamically generated SQL queries. This vulnerability allows attackers to modify the query structure, gain unauthorized access to data, or execute other database commands. The vulnerable application interprets the user input as executable code. This opens the door to one of the most common and dangerous web security issues.
SQL Injection Example
The example is provided for educational purposes for security professionals to better understand how to prevent such attacks. This post does not encourage illegal actions.
Before getting into the reasons behind the SQLi, here is a simple example in PHP with a vulnerable query during the login process. It can be assumed that the username and password were taken from the submitted login form, and these values were directly inserted into the SQL query string as follows:
$username = $_POST['username'];
$password = $_POST['password'];
$query = "SELECT * FROM users WHERE username = '$username' AND password = '$password'";Typically, an application would send such a query to the database, and if the result is not empty, the credentials are valid. To bypass this check, an attacker could insert a SQL injection payload as the username, as in this code fragment (ending with a comment character to bypass the rest of the query after the injection):
' OR 1=1;--The resulting SQL query:
SELECT * FROM users WHERE username = '' OR 1=1;-- AND password = ''Since the 1=1 condition is always true and the password check is commented out, this query bypasses authentication and could provide unauthorized access. Adding basic validation will help make the attack more difficult, but the right solution is to use parameterized queries that clearly separate user input from the code being executed.
Causes of SQL Injections
While the primary cause of SQL injections is the unsecure handling of user input in SQL queries, there are additional factors that contribute to this vulnerability. Understanding them helps identify weaknesses in early application development.
Insufficient input validation and sanitization
If an application does not validate or sanitize user input, an attacker can insert SQL statements into fields intended for regular data. Without validation, it cannot distinguish between legitimate and malicious data, allowing dangerous commands to enter the database.
Incorrect use of dynamic SQL
Forming SQL queries by concatenating strings (joining two or more strings into one) with user input poses a high risk. Constructing a query in this way incorporates raw user input into the query logic, allowing attackers to manipulate it. Using parameterized queries or prepared statements is a safer alternative that ensures the separation of code and data.
No context-aware encoding
The encoding of the output data should be appropriate for the context in which it is being used. For example, HTML encoding is appropriate for web pages, but SQL query input should be encoded appropriately as part of the parameterization process, not manually. Incorrect or omitted encoding when constructing a malicious query significantly increases the risk of injection, as the database or application may not properly neutralize the input.
Risky legacy code
Old applications often use hard-coded SQL logic and outdated development practices. They may not validate input data, use dangerous coding constructs, or even have old versions of databases with known vulnerabilities. Without updates, these applications become a constant source of risk.
Excessive database privileges
If an application connects to a database with administrative or elevated privileges, an attacker can gain access to system tables that are not intended for use. In such a situation, any successful injection can cause significant damage. Limiting database privileges to only what is necessary for each operation is a critical to reduce the impact of potential exploits. This also includes running the database process itself from a restricted account rather than root.
Improper error handling
Providing users with detailed error messages can give attackers insight into the structure of the database, making it easier to create successful SQL injection payloads. Proper error handling ensures that internal problems are securely logged while only returning general messages to end users. In some cases, attackers can also detect errors indirectly based on changes in database response times, allowing blind SQL injections.
Insufficient security testing
Without regular security testing, SQL injections are easy to miss. Static analysis is a first step, but code review alone cannot predict how user input will be processed in queries. Any gaps in dynamic security testing, whether automated or manual, significantly increase the risk of undetected vulnerabilities entering production.
Preventing SQL Injections with DAST
The most effective way to prevent SQL injections is to combine secure coding practices with testing running applications. This is where DAST (Dynamic Application Security Testing) plays an important role.
The DAST approach, supported by Invicti (formerly Netsparker), allows teams to see real risks that can be exploited by testing applications in real-world conditions. Using proof-based scanning technology, Invicti automatically confirms found vulnerabilities, reducing false positives and speeding up remediation.
By integrating DAST into the development process, organizations can detect and remediate SQL injections before they are exploited by an attacker — a practical and scalable strategy for combating one of the oldest, yet still most dangerous, web security threats.
