Common or uncommon, its extremely unprofessional. You know when you are dealing with a kid or with professional who actually wants to get hired and has some manners.

Sharing other's company secrets by mistake, using other company's resources in ways that are definitely forbidden - is this a person you really want to hire since they will behave the same in your company? Is this a person you want to give trust with some internals?

In market with 100s or applicants thats enough to disqualify anybody who actually needs an interview or two to get hired.