-1' OR 5*5=25 or 'DjalrbRJ'='

That looks like an SQL injection payload. It’s trying to break out of a string literal in a query and inject a tautology to bypass logic (e.g., authentication).

What it does, in simple terms:

• -1' ends a string literal in the SQL query.
• OR 5*5=25 is a boolean condition that’s always true.
• OR 'DjalrbRJ'=' adds another condition and is often used to test if the input handling is robust (the exact trailing part is incomplete, but the idea is to extend the injection).

If the application builds SQL by concatenating user input without parameters, this could cause the WHERE clause to evaluate to true and return data or bypass login.

Defensive practices (definitely exam-relevant):

• Use parameterized queries (prepared statements) instead of string concatenation.
  • Examples (conceptual):
    • Python with psycopg2/MySQLdb: cursor.execute("SELECT * FROM users WHERE username = %s AND password = %s", (username, password))
    • PHP with PDO: $stmt = $pdo->prepare("SELECT * FROM users WHERE username = :user AND password = :pass"); \(stmt->execute(['user'=>\)username, 'pass'=>$password]);
    • Java with PreparedStatement: PreparedStatement ps = conn.prepareStatement("SELECT * FROM users WHERE username = ? AND password = ?");
• Hash passwords and compare hashes (never store or compare plain passwords).
• Validate/whitelist inputs and enforce length limits.
• Use least-privilege database user accounts.
• Consider additional defenses: input sanitization as a secondary layer, Web Application Firewall (WAF), and proper error handling (don’t reveal DB errors).
• Prefer ORM or query builders that automatically parameterize inputs.

If you want, I can show a small, concrete before/after example in a language you’re studying (e.g., Python, PHP, Java) to illustrate how to defend against this kind of payload.