Crossrider, aka OSX/Shlayer is a type of adware which infects Macs via a fake Adobe Flash Player installer. The virus is also known as a new version of the OSX/Shlayer malware.
During the installation process, the fake Flash Player installer leaves a copy of Advanced Mac Cleaner which uses Siri’s voice to tell you that it has found problems with your computer. Most probably, this is caused by a configuration profile installed on the system by Crossrider. Thus, you should be very careful when you install new programs on your Mac.
In case you see a message on your screen saying that Adobe Flash Player should be updated, it’s almost certainly a scam. To check if there are any updates for your Flash Player, you have to visit the Adobe’s official website: https://get.adobe.com/flashplayer/
Keep in mind that the installation of third-party software is not safe for your Mac, unless it’s from the App Store or identified developers, as per the Security & Privacy settings, which you can access this way:
System Preferences > Security & Privacy > General