-1' OR 5*5=25 --

What you posted is a classic SQL injection payload.

• What it does: It tries to terminate the current string in a SQL query, injects a tautology (5*5=25, which is always true), and uses a SQL comment (--) to ignore the rest of the query. This can cause the WHERE clause to always evaluate to true, potentially bypassing authentication.

• Why it works: If user input is directly concatenated into a SQL statement, the input can alter the logic of the query rather than just be treated as data.

• Defensive takeaways (exam-ready):

  • Never build SQL by concatenating user input. Always use parameterized/prepared statements.
  • Use a database API that supports placeholders and pass user input as parameters.
  • Consider ORM/query builders that automatically parameterize queries.
  • Enforce least-privilege database accounts and avoid exposing detailed error messages.
  • Validate and sanitize input, but don’t rely on validation alone for security.

• Quick examples (conceptual, language-agnostic):

  • Vulnerable (unsafe):
    • query = "SELECT * FROM users WHERE username = '" + username + "' AND password = '" + password + "'"
  • Secure (safe):
    • query = "SELECT * FROM users WHERE username = ? AND password = ?"
    • bind parameters: (username, password)

• Short language snippets (illustrative):

  • Python (sqlite3/psycopg2 style): cursor.execute("SELECT * FROM users WHERE username = ? AND password = ?", (username, password))
  • Java (PreparedStatement): PreparedStatement ps = conn.prepareStatement("SELECT * FROM users WHERE username = ? AND password = ?"); ps.setString(1, username); ps.setString(2, password);
  • PHP (PDO): $stmt = $pdo->prepare("SELECT * FROM users WHERE username = :username AND password = :password"); $stmt->execute(['username' => $username, 'password' => $password]);

• Important note: Do not test injection on systems you don’t own or have explicit permission to test.

If you want, tell me your language of choice and I’ll tailor a secure example handout for your exam notes.