source: http://www.securityfocus.com/bid/24598/info

Apple WebCore is prone to a cross-site scripting vulnerability because the application fails to properly sanitize user-supplied input.

An attacker may exploit this issue by enticing victims into visiting a malicious website.

The attacker may leverage this issue to execute arbitrary script code in an application using the affected framework (typically Safari). This may help the attacker steal cookie-based authentication credentials and launch other attacks. 

xmlhttp.setRequestHeader('Foo', 'baa\nHost: test\n');

The above request is treated as valid and results in:

GET / HTTP/1.1
Accept-Encoding: gzip, deflate
Accept-Language: en
Foo: baa
Host: test 