One advice that is generally dispensed to prevent your computer from getting infected by malware or a trojan is to simply not download any file attachments you get in your emails by people you do not know. However, sometimes these attachments might look harmless, like a Microsoft Word or Excel file.
However, it seems that according to former NSA hacker Patrick Wardle, he has discovered a flaw in which a hacker could potentially take over a Mac computer by the user double clicking and opening a Microsoft Office file. This hack actually strings together multiple exploits to pull it off, one of which involves using a legacy file format and also macros.
However, as Wardle notes, this isn’t necessarily an easy hack to pull off as it would require that the user has to log into their Mac computers in two separate occasions, as each occasion will trigger a different step in the process, but he believes that since this hack can be easily distributed, there is a good chance that at least a couple of people might fall for it.
The good news is that if you run Microsoft Office on your Mac computer, both Apple and Microsoft have since addressed the flaw in the latest versions of macOS and Office for Mac respectively, so you’ll want to make sure you have the latest update if you don’t want to leave yourself vulnerable.