I am a software tester. I would like to know the techniques to fool the code and get defects in the code. I prepare some test data for different data types like numeric, character, dates etc.

I would like to know if there are any ways to fool the code or the developers and get defects.

I need to check the data validations and looking to get defects.

Are there any ways to disguise the data from simple validations on a web browser ?

Pleae help. ******ly required.