It is notoriously dangerous to use wireless connections in places such as coffee shops and airports. An attacker could intercept your connection using a "man-in-the-middle" (MITM) attack and steal your personal data including your credit card information.
Make sure to never input your card details while surfing the Internet from a public WiFi hotspot, or as they say "do it at your own peril".
Also, if you regularly visit any websites, be sure to update your passwords to safeguard from security leaks that would allow scammers to access your information.