Apple Inc (AAPL.O) said the vast majority of Mac computer users are not at risk from the recently identified “Shellshock” computer bug, which security experts have warned affect operating systems, including Mac’s OS X. “The vast majority of OS X users are not at risk,” Apple spokesman Bill Evans said late Thursday evening. “Shellshock” is a vulnerability in Bash, a piece of software packaged with Mac OS X, which is based on the Unix operating system.