Victims get tricked into installing trojans, other malware that spreads via fake codecs. Ransomware is one of the types that can also be distributed using such a method. Researchers always find various malware that spreads using fake codecs and can disable antivirus products to make users believe that the tool is still running and keeping the system safe while the malware runs its processes.
Such malware that spreads around with the help of fake codecs can also find its way on macOS devices. Reports have surfaced a few times in the last decade or so that malware versions posing as false ActiveX objects were found on various sites. Social engineering is also the method used in such campaigns.