What Is SQL Injection? Detection Examples and Prevention

SQL injection (SQLi) is a code injection attack that exploits applications constructing SQL queries from unsanitized user input. An attacker injects malicious SQL statements into input fields, altering the query logic executed by the database.

Classified as OWASP A03:2021 – Injection and mapped to CWE-89, SQL injection has been a top web vulnerability for over two decades. A successful attack can allow an attacker to read, modify, or delete arbitrary database records, bypass authentication, execute administrative operations, or in some cases run operating system commands on the server.

SQLi is language-agnostic. Any application that builds SQL queries from user input—whether written in JavaScript, Python, Java, Go, or TypeScript—is vulnerable if proper parameterization is not used.

SQL injection exploits the boundary between data and code. When user input is concatenated directly into a query string, an attacker can break out of the data context and inject SQL commands:

const query = "SELECT * FROM users WHERE username = '" + username + "' AND password = '" + password + "'";

If an attacker enters ' OR '1'='1' -- as the username, the resulting query becomes:

SELECT * FROM users WHERE username = '' OR '1'='1' --' AND password = ''

The database cannot distinguish between the developer's intended SQL and the attacker's injected SQL—both are parsed as a single statement.

Attack Variants

• Union-based: Uses UNION SELECT to extract data from other tables
• Error-based: Forces database errors that reveal structure and data
• Boolean-based blind: Infers data from true/false response differences
• Time-based blind: Uses SLEEP() delays to extract data one bit at a time

SQL injection has caused some of the largest data breaches in history:

• Heartland Payment Systems (2008): SQLi led to the theft of 130 million credit card numbers and over $140 million in settlements.
• Sony Pictures (2011): Union-based SQL injection exposed 1 million user accounts with plaintext passwords.
• TalkTalk (2015): A teenager exploited SQLi to steal 157,000 customer records. The company was fined £400,000 and lost over 100,000 subscribers.

These incidents share a common pattern: SQL injection was a known vulnerability with established defenses, yet it persisted due to inconsistent coding practices and insufficient automated detection.

CodeSlick detects SQL injection patterns across all five supported languages—JavaScript, TypeScript, Python, Java, and Go—in under 3 seconds.

• String concatenation and template literals used to build SQL statements with user-controlled variables
• ORM escape hatches like sequelize.query(), knex.raw(), cursor.execute() with formatted strings, and Statement.execute() in Java
• Missing parameterization in queries using variable interpolation instead of placeholders (?, $1, :param)

All SQL injection findings are rated Critical (CVSS 9.8) with CWE-89 classification and OWASP A03 mapping. CodeSlick's AI-powered fix suggestions generate secure parameterized alternatives specific to your code context.