What common mistake do developers make with Query parameters, why does the mistake cause problems, and what is the safer approach?

What common mistake do developers make with Query parameters, why does the mistake cause problems, and what is the safer approach? One recurring problem with query parameters is applying it without understanding the boundary it protects. Trusting raw input and using it directly in database updates or application decisions without validation and authorization. In addition, Query-string values can be read independently from form payload values. Safer engineering approach: keep the responsibility in the correct layer, use the framework's supported API, validate and authorize inputs, avoid hidden side effects, and verify the behavior with tests.