-1' OR 3*2>5 --

This looks like a SQL injection payload. Here’s what it does and why it’s dangerous, plus how to defend.

What the string does

• The part -1' ends a quoted string literal in SQL.
• Then OR 32>5 adds a condition. 32 equals 6, and 6>5 is true.
• The -- at the end starts a SQL comment, so the rest of the original query is ignored.
• Overall, the WHERE clause becomes something like: username = '-1' OR true, which makes the condition always true (in effect, bypassing the intended filtering).

Why this matters

• If a query is built by concatenating user input, this can bypass authentication or reveal more data.
• The exact behavior can vary by database (boolean results, how comments are parsed), but the core idea is injecting a condition that’s always true and commenting out the remainder.

Defensive measures (exam-ready basics)

• Use prepared statements / parameterized queries with bound variables instead of string concatenation.
  • Example (illustrative):
    • Python (sqlite3/psycopg2): cursor.execute("SELECT * FROM users WHERE username = ? AND password = ?", (username, password))
    • Java: PreparedStatement stmt = conn.prepareStatement("SELECT * FROM users WHERE username = ? AND password = ?"); stmt.setString(1, username); stmt.setString(2, password);
    • PHP (PDO): $stmt = $pdo->prepare("SELECT * FROM users WHERE username = :u AND password = :p"); $stmt->execute([':u' => $username, ':p' => $password]);
• Do input validation and allowlist user input where appropriate (e.g., usernames that match a pattern).
• Use least-privilege database accounts (no broad SELECT/UPDATE/DELETE rights beyond what’s needed).
• Consider ORM layers or frameworks that automatically parameterize queries.
• Disable verbose error messages that could reveal SQL structure.

If you’d like, I can tailor examples to a specific language or database you’re studying (e.g., MySQL, PostgreSQL, SQLite) and show a vulnerable snippet vs. a fixed snippet side by side.