A fake Safari update prompts you to install MacKeeper and ZipCloud. Both Chrome and Firefox browsers had their home pages and search engines set to a Yahoo Search BOSS page. The new version of the InstallCore installer was obtained while visiting one of the First Row Sports scam sports streaming sites. It also installed a newer version of Safari and a number of Safaris support files! This, of course, had the effect of completely breaking Safari on my 10.9.5 system, as the newer version cannot run on that version of OS X.”]
Source: https://blog.malwarebytes.com/cybercrime/2015/07/fake-safari-update-installs-mackeeper-zipcloud/