The code that is run on the user's computer can be used to download and infect it with a virus, Trojan horse, or some other malware. The vulnerabilities can also cause Safari to crash.
The new Safari versions, update or patch are: Safari 6.1.4 for OS X Mountain Lion and Safari 7.0.4 for OS X Mavericks
This update can be downloaded and installed using Software Update, or from the Apple Support website.
For more information about the Safari Webkit vulnerabilities, click here