Can malicious code be posted on codepen.io or jsfiddle.net?

Question

JavaScript

For example, when you open a link, the code is immediately executed and steals personal data.

Answer 1

Um, what personal data? Paranoid
_ _

Answer 2

may
or may not be

Answer 3

Maybe.
Just because you can guarantee its absence only by being the administrator of this site, who has full access to it.