Security concern

Hi, I would like to know how secure is account of virtualmin? I have several domain accounts that are constantly hacked because of pour and buggy modules of CMS of the websites. And my main concern is that other clients domains accounts won’t be reached from these buggy sites. Is that situation possible? Can virus uploaded to /home/userA/domainX/Public_html can reach /home/userB/domainY/Public_html ?