When you run the installer, it will detect your old iTunes version. Choose Repair when prompted. This will repair the Apple Software Update, and reinstall and update iTunes to the latest version.

This latest iTunes update also delivers a security fix, dealing with a vulnerability ... allowing iPhone and iPad users to ...

Click "Update." At this point, iTunes will try to repair the operating system without erasing any of the apps or data on the device. 7. If the update process fails, you can repeat the procedure ...