Comex has released the source for his PDF exploiting website www.jailbreakme.com (story here)

This means that anyone can setup their own site that does anything they want to on your iPhone/iPod/iPad as soon as you go to it.

1.) If you are not jailbroken and do not need to be, please update to the latest firmware as soon as possible (TODAY -or- before you use your iPhone to surf the Internet).

2.)If you are jailbroken and want to stay as you are, you MUST install “PDF Patcher 2″ from Cyda as soon as possible (TODAY -or- before you use your iPhone to surf the Internet).

There is a very dangerous exploit (the one used to jailbreak phones), which has just been released to the public.

Using this exploit anyone controlling any web page you go to could do anything to your phone. That could range from completely deleting all your data after stealing it, or installing things like password stealers.

Your iPhone/iPod/iPad is *NOT* safe to surf the web with unless you have done one of the 2 above things. 

Of course, if you want to jailbreak (which you should!), here’s how

IF You have an iPhone with firmware version lower than 4.3.3, you can jailbreak it directly from the device by going to http://www.jailbreakme.com/

Here are instructions for jailbreaking 4.3.4 -

Note : This is a tethered only jailbreak, which means if your phone reboots it will not work again until you connect it to a computer and re-run redsn0w.

You will need the iPhone 4.3.4 ipsw file, download from Apple, links here, which iTunes probably already downloaded, but will auto delete when it’s no longer current.

http://www.redmondpie.com/jailbreak-4.3.4-ios-iphone-4-3gs-ipod-touch-4g-3g-ipad-with-redsn0w-how-to-tutorial/

I used redsn0w and it had a few quirks, you may want to try one of the other tools.

http://www.redmondpie.com/jailbreak-4.3.4-ios-iphone-ipad-ipod-touch-using-pwnagetool-bundle-how-to-tutorial/

iOS has had a long history of security holes, which people who like to jailbreak are grateful for. The entire iOS community has been very lucky for how big it is and how many  vulnerabilities there have been, and how few actual uses.

I highly recommend you donate to some of the iOS jailbreak developers, their website is here. If they can make good money using exploits for the common good, the less incentive they will have to use their smarts for profitable evil!

Enjoy.