Since the jailbreak for iPhone 4 was announced, reports have been circulating that there is a large hole in iOS4 that would allow malicious hackers to gain access to an iPhone 4 device and install software.
The security flaw in iOS4 exploits the manner in which the Safari web browser in iOS4 manipulates PDF files and several security experts have described it as a very dangerous problem. Apple has not yet offered a fix for the flaw but is apparently looking into it. Unfortunately, until they do offer a patch, users with iPhone 4 devices remain susceptible to third party attack, especially now that this flaw is so well known.
If you are concerned about this flaw and don’t wish to wait for the Apple fix then, ironically, if you jailbreak your device using the website (which exploits the Safari flaw) and install an app package from Cydia called ‘PDF Loading Warner’, you can attenuate the threat. The app does not completely fix the security flaw but does warn you if Safari tries to load a PDF file which, by circumventing the normal iPhone security procedures, can result in the security hole being exploited.