What SQL injection is
SQL injection is a web security vulnerability in which an attacker interferes with the database queries that an application makes, by supplying malicious input. Many applications build database queries using data that users provide. If that input is not handled carefully, an attacker can craft it so that it changes the meaning of the query, letting them manipulate the database in unintended ways.
How the attack works
SQL injection happens when user-supplied input is combined into a database query without proper handling. An attacker provides input designed to be interpreted as part of the query's commands rather than as mere data. If the application inserts this input directly into the query, the attacker's commands become part of what the database executes, which is how the injection takes effect.
What an attacker can achieve
Through SQL injection, an attacker may be able to access data they should not see, modify or delete data, or otherwise interfere with the database behind an application. Because databases often hold sensitive information, this can be very damaging. The ability to manipulate queries gives the attacker influence over the application's core data, making SQL injection a serious vulnerability.
Why input handling matters
The root cause of SQL injection is treating untrusted input as if it were trusted parts of a query. When input that should be plain data is allowed to change the structure of a query, the vulnerability arises. This is why careful handling of user input is central to preventing SQL injection: the application must keep data separate from the commands of the query.
Preventing SQL injection
A well-known defense against SQL injection is to use parameterized queries, where user input is passed as data that cannot alter the query's structure. By keeping the query's commands fixed and treating input strictly as values, the application prevents injected input from changing what the query does. This separation of code and data is the primary way SQL injection is avoided.
Why it matters
SQL injection is one of the most important web security vulnerabilities to understand. Knowing what it is - manipulating an application's database queries through malicious input - clarifies why careful handling of user input is essential. For anyone interested in web security, it is a valuable concept to understand.
Related on Skillo
See also: What is a database query? Explained, What is SQL? Explained.
Sources
Published date reflects the original event date (2026-05-19). This article is original Skillo editorial written from the sources above; facts were verified in September 2026.
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