snap install skype

When you run "snap install skype" in terminal without the quotes, you get the following message:

x@y:~$ snap install skype
error: This revision of snap "skype" was published using classic confinement
       and thus may perform arbitrary system changes outside of the security
       sandbox that snaps are usually confined to, which may put your system at
       risk.

       If you understand and want to proceed repeat the command including
       --classic.
x@y:~$

What kind of risk is the system being potentially subjected to?

Please explain and provide in-depth links on the subject matter.