Here's a warning)))) I did it for my iPhone 3Gs and after several mins I decided I did not want it ...so I did a reset of my phone and all hell broke loose , 1st it froze for 6hrs so I called apple and they walked me thru some steps that got my iPhone working to it's "factory default" but now I connect to any wi-fi or if I have more then 10 pic they get erased by it self :-( ....
PS: but I do have friends that have it with no problems ,just be VERY careful !!!
well jailbreaking is ALWAYS at your own risk, i did this with my 3gs on firmware 3.1.3 and it worked with no problems and currently using it right now, no problems yet
Looks like Apple sent the upgrade out to plug the exploit used by PDF files. Once this became public anyone could write malicious code and execute it the same way.
If you saved your hashes through Saurik Server then you can always downgrade, I have successfully done that in the past.
If you want to protect your jailbreak iPhone there is a Cydia app that warns of any PDF file before it opens. Its called PDF Loading Warner on the BiggBoss repo.
I tried Ultrasnow but noticed it was buggy also.
modmyi.com is another great place for hacking info.