dup/clone and taintedness

I was reading this:

"these methods allocate a new instance of the class of the object on
which they are invoked. They then copy all the instance variables and
the taintedness of the receiver object to the newly allocated object."

What does it mean "taintedness"?

thanks for response

Taintedness refers to a default lack of trust in a value that was obtained from an unknown source. (Typically user input of some kind.)