You prepareStatement is still vulnerable if you do like this

String sql = "SELECT *FROM users WHERE username = '" + userInput + "'";

PreparedStatement pstmt = connection.prepareStatement(sql);

is this code vulnerable? I am using prepared statement.

The Vulnerability

You are incorrectly building the SQL query string before passing it to connection.prepareStatement().

1. Vulnerable Code:Java

   String sql = "SELECT * FROM users WHERE username = '" + userInput + "'"; // ❌ Flaw here
   PreparedStatement pstmt = connection.prepareStatement(sql);
   

2. The Flaw: By concatenating userInput directly into the sql string, you are treating user input as part of the SQL command's structure. If an attacker enters a malicious string like ' OR '1'='1, the resulting query sent to the database is:SQL

   SELECT * FROM users WHERE username = '' OR '1'='1'
   

   This bypasses authentication because the OR '1'='1' clause evaluates to true for every row.

✅ The Correct Fix

To use PreparedStatement securely, you must use a placeholder (?) in the query string and set the user input separately using a set... method.

1. Secure Code:Java

   String sql = "SELECT * FROM users WHERE username = ?"; // ✅ Use placeholder
   PreparedStatement pstmt = connection.prepareStatement(sql);
   pstmt.setString(1, userInput); // ✅ Set input separately
   // Now execute the query (e.g., pstmt.executeQuery();)
   

By using the placeholder, the database driver handles the userInput strictly as data, automatically escaping any malicious characters and eliminating the injection risk.