-1" OR 5*5=25 --

It looks like a classic boolean-based SQL injection payload.

What it does (in brief):

• The -1" is likely trying to break out of a string literal in an insecure query.
• 5*5=25 is a condition that evaluates to true.
• The OR 5*5=25 makes the overall WHERE clause true, potentially bypassing authentication checks.
• The -- at the end is a SQL comment marker, which ignores the rest of the query after that point, neutralizing any following conditions.

Why this is dangerous:

• If a login form or any query directly concatenates user input into SQL, an attacker can alter the logic of the query and gain unauthorized access.

Defensive measures (exam-friendly essentials):

• Use parameterized queries/prepared statements for all user inputs (avoid string concatenation to build SQL).
• Validate and sanitize inputs, but don’t rely on sanitization alone.
• Use least-privilege database accounts (no rights beyond what’s needed).
• Prefer stored procedures with parameters and avoid dynamic SQL when possible.
• Implement input validation and proper error handling; don’t reveal database errors to users.
• Regularly test with security-focused code reviews and dynamic/static testing.

If you want, I can turn this into a short exam-style question or walk through a safe, secure coding example showing how to write a login query with parameters.