Pass value to form field &amp problem

Hi, I have a problem with passing parameters to forms using plug in because the editor turns & into &

For example

{chronoforms5}order&product=myproduct{/chronoforms5}

becomes

{chronoforms5}order&product=myproduct{/chronoforms5}

and obviously the field doesn't get the value. I use to read a solution by editing some code but I cannot find the post anymore.

Could you please suggest me what file I should edit and what lines?

Thank you.