Is it dangerous to charge your smartphone using public USB charging stations in airports and malls?

YES, HACKERS CAN INJECT MALICIOUS CODE OR READ DEVICE MEMORY THROUGH THE USB PORT.

Public charging stations use standard wired interfaces that support simultaneous power delivery and data exchange. A modified cable or hidden controller can intercept files from a connected device.

Juice Jacking Attacks and Hidden Data Theft

A smartphone's standard USB port combines power pins with a digital data bus. When connected to a compromised charging port, a hidden microcomputer mimics a trusted device connection and sends service commands to extract photos, message caches, and session tokens.

How to Protect Your Device When Charging Away from Home

Use your own wall charger and plug only into standard AC power outlets.
Use a USB data blocker adapter that physically disconnects the data transfer lines.
Lock your smartphone screen and select the "Charging Only" mode.
Use a portable power bank instead of connecting to untrusted cables.