Fix the PDF Exploit (cydia app)
 

Comex used a PDF exploit to jailbreak iOS 4 on all devices, but evil-doers can also use this exploit to get malicious code into your phone.

You can fix this patch on your jailbroken iPhone by searching/installing "PDF Patch" This way you don't have to update to 4.0.2 and lose all jailbreak options.

(thanks redmondpie)

Re: Fix the PDF Exploit (cydia app)
 

Which top Cydia app i can use for my iPhone?