I had used my laptop computer while traveling. Although i did not log into PayPal, I did log into my e-mail account. My e-mail and PayPal had the same password. Since PayPal uses e-mail addresses as user ID, the hacker took a chance and scored. PayPal security noticed it rather quickly and reversed the charges.

I did not have a credit card associated with the account, though.

Moral of story: use different passwords for e-mail and PayPal, in case the hackers get your e-mail info.