Brian thinks his Mac got hit by malware. He clicked on a link that took him to a page saying his Adobe Flash player was out of date, and he installed something. Now he thinks he's been busted. Leo says that Chrome has Flash built-in, and it's always updated, so he'll never have an outdated version.
Leo also says that Malware isn't really the issue here because Macs are not really subject to Malware like Windows. It's more likely a browser hijack plugin. He'll find them in the extensions, and it's simply a matter of deleting the extension and rebooting his browser. Given what may or may not be on there, if he's backed up, he should go into recovery mode and format the hard drive, then reinstall the operating system.