-1' OR 3*2>5 --

That looks like a classic SQL injection payload. Here’s the idea in a safe, exam-focused way:

• What it does (in a vulnerable app):

  • If the user input is concatenated into a SQL query, the input -1' OR 3*2>5 -- can break out of a string literal and inject SQL.
  • 3*2>5 evaluates to true (6 > 5 is true).
  • The -- starts a comment, so the rest of the original query is ignored.
  • Resulting effect (conceptually): the WHERE clause becomes something like where username = '-1' OR 6>5, which is always true, so the query returns all rows (bypassing authentication).

• Why this works: it relies on the string being unsafely concatenated into SQL without parameterization.

• How to defend (exam and real-world practice):

  • Use parameterized/prepared statements for all SQL queries.
  • Do not concatenate user input into SQL strings.
  • Validate and whitelist input where appropriate.
  • Use ORM or query builders that automatically parameterize.
  • Apply least-privilege database accounts and proper error handling.

• Quick examples of safe usage:

  • Python (sqlite3, psycopg2): cursor.execute("SELECT * FROM users WHERE username = ?", (user_input,))
  • PHP (PDO): $stmt = $pdo->prepare('SELECT * FROM users WHERE username = :username'); $stmt->execute(['username' => $user_input]);
  • Node.js (mysql2): connection.execute("SELECT * FROM users WHERE username = ?", [user_input]);

If you want, I can tailor a short, exam-style answer or a checklist for SQL injection defense.