If you rely on a third-party file manager with an iOS device, hold off on installing iOS 8.3, since new security settings disable many of these apps. Utilities such as iFunbox, iTools, and iExplorer are all affected. iFunBox and iExplorer have been updated to sidestep the new security settings, but with the limitation that they work only with apps that use iTunes File Sharing. follow link
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iOS 8.3 Blocks File Managers and Transfer Utilities