Apple’s AirDrop is a feature that allows you to send photos and other documents between iPhones and iPads. It uses Bluetooth for the exchange, so the devices need to be close to each other. If you aren’t familiar with the feature, but it sounds helpful, here is Apple’s How To support page on it.
Computer Science researchers discovered a flaw in AirDrop. As a result, unauthorised strangers can find email addresses and phone numbers. The researchers have also suggested a way to improve security.
The recommendation of security experts is to set AirDrop to “Receiving Off” until you need to use it for a specific reason. Once you have shared your document, you should then turn it off immediately. When activated, try to limit your use to "Contacts Only". Whilst you will sacrifice some convenience doing this, you will be adopting a security-first mindset and making your use of tech more secure.