It was recently found at a Cryptopath website that the iPhone could be exploited using the certificates that Mobile Safari handles. It can be exploited by creating your own certificated disguised as Apple’s, a hacker can gain access to the root-level settings, which can allow an attacker to grab data off the iPhone (such as saved SMS, voicemails, etc). But, what the attacker can’t do is remotely run or install applications. The reason that the iPhone and iPod Touch certificates can be exploited, is because the VeriSign doesn’t actually check the warnings that the signature checks give, it basically ignores them. It’s not being currently used, but it may soon be used in the near future (hopefully it will be implemented in a 3.1.3 iPhone or iPod Touch jailbreak 
).
Source: http://www.macobserver.com/tmo/article/iphone_vulnerable_to_security_certificate_flaw_attacks/%5C/
