This can be exploited by malicious websites to display custom URLs, potentially fooling users into supplying personal information to a malicious website. This is because the Safari address bar can display a totally different address than the website that is actually being displayed.
MajorSecurity has notified Apple of the issue and it is at the point where it is likely just a matter of time before a patch is available to fix the problem. Apple is working to fix this issue. However, it is probably a good idea to avoid opening untrusted links. Please do not give out your personal information to any website that asks for it through Safari on your iOS device.