The claim from Apple Website

Security
Now you can enjoy worry-free web browsing on any computer. Apple engineers designed Safari to be secure from day one.

The reality

http://www.infoworld.com/article/07/06/11/Safari-for-Windows-released-and-hacked-in-a-day_1.html

Safari for Windows: Released and hacked in a day
Hours after the beta of the Safari browser for Windows was released, researcher Aviv Raff posted that he had found a bug -- and that it only took him three minutes to do so.

Apple is becoming a favorite target of security researchers these days. In April, there was the $10,000 CanSecWest hack a Mac contest, and on Monday, there was the Safari Web browser. Or the public beta of Safari for Windows, anyway.
Just hours after Apple released its first Windows beta of Safari, researcher Aviv Raff said he'd found a bug.

In an interview, Raff said that it took about three minutes of fuzzing to find the bug and that he hadn't tested the issue on Mac OS X. So he couldn't say whether or not it affected Safari on Windows only. The bug causes the browser to crash and "might be exploitable," according to Raff, meaning it could possibly be used to run malware on the PC.

Raff was clearly unhappy with Apple's claim that Safari was designed to be "secure from day one" (he called this claim "pathetic"), but he said he wasn't particularly going after Apple. "I don't pick just on Apple," he said. "I've posted about Microsoft and Mozilla issues too."

"Everyone has bugs, but not everyone says that they are 'designed to be secured from day one,'" he added. "I guess it's day zero now."