-1' OR 172=172 or 'mg6zfHtx'='

This looks like an SQL injection payload. The idea is to break out of a string literal in a SQL query and inject a condition that's always true, so the query returns data (or logs in) without proper authentication.

What the parts do (in a typical vulnerable query)

• -1' ends the current string literal and injects extra SQL.
• OR 172=172 is a tautology (always true).
• or 'mg6zfHtx'=' is another fragment that would compare two strings (likely intended to be false, but the previous tautology makes the overall condition true).

A simplified example:

• Original vulnerable query (in code, not a safe practice): SELECT * FROM users WHERE username = '$username' AND password = '$password';
• If an attacker supplies username = -1' OR 172=172 -- The query becomes: SELECT * FROM users WHERE username = '-1' OR 172=172 --' AND password = '$password'; Since 172=172 is always true, the WHERE clause is effectively true for all rows, so the attacker may bypass authentication.

How to defend (exam-relevant best practices)

• Use parameterized queries / prepared statements everywhere:
  • Do not concatenate user input into SQL strings.
• Use an ORM or safer database access layer that binds parameters.
• Validate and sanitize input, and apply allowlists (whitelist allowed values and types).
• Enforce least privilege on the database user used by the app (no SELECT *; restrict to needed tables/columns; no drop/alter permissions).
• Use stored procedures with parameterized inputs where appropriate.
• Implement input length checks and type checks (e.g., expect a username as a specific length/character set).
• Consider a Web Application Firewall (WAF) as an additional layer, and keep frameworks and DB drivers up to date.
• Avoid dynamic SQL generation entirely when possible.

If you’re studying for an exam, you can be asked to:

• Identify that a payload is attempting an SQL injection.
• Explain why it works (tautology like 1=1 or 172=172 makes the condition always true).
• Describe how to fix it (prefer prepared statements, parameter binding, input validation, and least-privilege DB access).

If you want, I can tailor this to a specific language or framework (e.g., PHP with mysqli, Python with psycopg2, Java with JDBC) and show concrete safe code examples.