Kaspersky reports that 1 in 10, or 10%, of Apple computers have been attacked by the Shlayer Trojan. The malware is a global threat with victims throughout the world and lion share of victims are located in the USA. When visiting these fake web sites, instead of being greeted with a video to watch, they are told they need to first update Flash Player. When executed, the Trojan will install a malware cocktail onto the computer. It installs a malicious browser extension that monitors your search and browsing activity and redirects you to other search engines.
Source: https://www.bleepingcomputer.com/news/security/10-percent-of-all-macs-shlayered-malware-cocktail-served/