The Mac Observer is reporting on a vulnerability issue related to Mobile Safari on iPhones and iPads running iOS 5.1. Earlier versions may be affected as well.
The vulnerability allows malicious sites to display a false URL in the Safari address bar. This could trick users into entering login credentials or other sensitive information on a webpage thinking that it was a legitimate site.
His recommendation is to upgrade Safari once Apple provides a resolution for this issue. At this time, Apple has made no comment regarding the vulnerability.