-1' OR 5*5=26 or 'mg6zfHtx'='

It looks like a tiny SQL injection payload. They’re typically used to try to break out of a string literal in a query and append extra conditions.

What the pieces suggest

• -1' attempts to close a string literal that was started in the query.
• OR 5*5=26 is a boolean expression (25=26) that is false.
• or 'mg6zfHtx'='" looks like another attempt to create a boolean check, but the trailing part is incomplete and would usually cause a syntax error.

In a vulnerable query like SELECT ... WHERE username = '$input' AND password = '$input2' this could cause the input to be treated as code, potentially altering the logic. In modern code, though, such an injection would almost always lead to a syntax error or, if the app is poorly designed, unpredictable results. It should not bypass authentication if the code uses proper protections.

How to defend in exams and real apps

• Use prepared statements / parameterized queries everywhere. Don’t concatenate user input into SQL.
• Validate and constrain inputs (whitelist allowed characters, enforce length limits, and reject obviously invalid formats for fields like username, IDs, etc.).
• Use least-privilege database accounts (no write access to read-only queries).
• Avoid dynamic SQL; use ORM/query builders that handle escaping.
• Handle errors securely (don’t reveal DB errors to users; log them server-side).
• Consider a Web Application Firewall (WAF) and regular security testing in a controlled environment.

Exam-oriented takeaway

• This payload demonstrates the basic idea of SQL injection (trying to alter true/false conditions via input). The exact outcome depends on how the query is built; with proper protections, it should be neutralized.
• Key concept to memorize: always treat user input as data, never as executable code, by using parameterized queries.

If you want, I can tailor a brief set of exam-style questions on SQL injection and defense or walk through safe code examples in your preferred language.