Apple has unexpectedly pushed out another update in the 4.3 series i,e 4.3.5 for iPhone 4, iPhone 3GS, iPod Touch 3G, iPod Touch 4G, iPad 1 and iPad 2 that fixes a security vulnerability with certificate validation. If you want to update your firmware to latest iOS 4.3.5, connect your device to your computer and open up iTunes. iTunes will automatically detect that new update 4.3.5 is avaialble for your device. Just click ‘Download and update’.
Direct Download links for iOS 4.3.5 firmware IPSW files