The Internationalized Domain Name (IDN) feature in Apple Safari before 5.1.4 on Windows does not properly restrict the characters in URLs, which allows remote attackers to spoof a domain name via unspecified homoglyphs.
Apple Security Advisory 2012-03-12-1 - Safari version 5.1.4 is now available and addresses 84 different vulnerabilities. This includes many fixes for WebKit related issues.