LG D959 - Manual (Page 138)

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NOTE: Your personal data—including information about your Google
account and any other accounts, your system/application data and settings,
any downloaded applications and your DRM licence —might be lost in the
process of updating your phone's software. Therefore, LG recommends that
you back up your personal data before updating your phone's software. LG
does not take responsibility for any loss of personal data.