-1' OR 581=581 or 'GH5LGdEn'='

That looks like an SQL injection payload rather than a normal query string. Conceptually:

• The snippet tries to end a user-supplied string in the SQL query and inject an always-true condition (for example, 581=581 is always true).
• The parts like -1' and or 'GH5LGdEn'=' are attempts to manipulate the SQL logic so that the WHERE clause evaluates to true regardless of the actual input.
• If the application concatenates user input directly into SQL, this can bypass authentication or reveal data.

Key exam points you can mention or need to know:

• What vulnerability this is: SQL injection due to unsafe string concatenation of user input into SQL queries.
• Why the payload can work: It closes the original string literal and adds an OR condition that is true, so the overall query matches.
• Consequences: Unauthorized login, data leakage, data corruption, or privilege escalation if the attacker can run other queries.

Best defense (how to fix in exams or real code):

• Use parameterized queries (prepared statements) for all user inputs:
  • Python (psycopg2, sqlite3): cursor.execute("SELECT * FROM users WHERE username = %s AND password = %s", (username, password))
  • Java: 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 = :u AND password = :p"); $stmt->execute([':u' => $username, ':p' => $password]);
  • Node.js (mysql2, pg, etc.): connection.query("SELECT * FROM users WHERE username = ? AND password = ?", [username, password])
• Do not build SQL by concatenating strings with user input.
• Hash passwords and store only the hashes (e.g., bcrypt, Argon2). Do not compare plaintext passwords.
• Validate and constrain inputs:
  • For numeric fields, cast/validate to numbers; reject non-numeric input early.
  • Use allowlists for expected values where appropriate.
• Apply least privilege: the DB user used by the app should have only necessary rights (no DROP/ALTER, limited SELECT/INSERT/UPDATE as appropriate).
• Avoid leaking error details to users; log errors server-side and show generic messages.
• Consider additional protections: input sanitization as a fallback, Web Application Firewall, and proper error handling.

If you want, I can give you a short, language-specific example or a quick mock exam question and answer about spotting SQL injection and fixing it.