NEVER USE PUBLIC USB CHARGERS!
If you are one of the millions who own a device like a phone, laptop etc. with a USB port then never charge these devices in public places such as Starbucks, airports or hotel lobbies. It's too risky and criminals target these public places like 'bees round a honey pot'.
Cyber criminals can easily modify USB charging ports and install malware on your device, they then have access to all your personal data including photos, text, emails and contacts. This cyber crime is called 'juice jacking'.
As a cyber security analyst once said “Plugging into an public USB port is kind of like finding a toothbrush on the side of the road and deciding to stick it in your mouth! You have no idea where that thing has been.”
This is an easy problem to solve though; just bring your own charger cord and plug it into a regular wall socket. Alternatively, use a 'power bank' to charge your phone and other devices.