-1' OR 3*2>5 --

This looks like a classic SQL injection payload.

What it does

• If user input is directly concatenated into an SQL string, "-1' OR 3*2>5 --" can break out of a string literal.
• The part 3*2>5 evaluates to true (6 > 5), so the WHERE clause becomes something like:
  • username = '-1' OR 3*2>5
  • which is effectively true for all rows due to the 6 > 5 condition.
• The -- comments out the rest of the query, potentially bypassing password checks and logging in without proper credentials.

Why this is risky

• It can bypass authentication or reveal data when user input is not safely handled.
• It relies on the database interpreting the input as SQL and on the app concatenating strings unsafely.

Defensive mitigations

• Use parameterized queries/prepared statements for all user inputs. Do not concatenate user input into SQL strings.
  • Example (conceptual): SELECT * FROM users WHERE username = ? AND password = ?
• Use proper placeholders in your language/framework (e.g., ? or $1) and pass values separately.
• Enable least-privilege database accounts (the app should not connect with an account that has more rights than needed).
• Disable execution of multiple statements in a single query if your DB driver allows it.
• Validate and sanitize inputs, and consider whitelisting allowed characters where appropriate.
• Use ORM or query builders that automatically parameterize inputs.
• Consider Web Application Firewall (WAF) and regular security tests, but don’t rely on them alone.

If you’d like, I can:

• Show a concrete before/after code example in your language of choice.
• Create a quick practice question for SQL injection defense.
• Explain how to test safely in a lab environment.