Thanks to Tom Limoncelli, I became acutely aware of USB charge-only cables and condoms. If you plug your phone into an unknown computer to charge the battery, you run the risk of having your phone hijacked by malware. USB transfers data as well as electricity and you’re essentially giving the computer unrestricted access to your phone.
Certain USB cables are charge-only and will not pass data. There are also “USB condoms”, which are inserted between the cable and the computer. They not only block data, but they can potentially charge the battery faster, as they can switch the device into a fast-charging mode. I’ve ordered a pair from Amazon, as we’re going to Europe in a week’s time.