Plug-ins can be a mixed blessing. On the one hand, they enable a bevy of features so that Mac users aren’t limited in their activities and the range of online materials they can view and access. On the other hand, though, a plug-in can be a weak link in one’s security set-up if it’s crudely designed or heavily targeted by malicious actors. To keep users safe, Apple may disable such known-vulnerable entities, displaying “Blocked Plug-in” alerts. These messages can also be shown by malware to tout additional infections.