How this happens

Recently my friend's account got hacked in paypal. He had 150$. First day he could see that he had only 50$. He did not understand anything and the very next day he could see his account empty. How this happens? Surely he did not share his password with anyone. But still how hackers were able to do this?

it may happened because he got not clean money or the senders charged back their money. It is annoying and possible, unfortunately ;/

More likely he was a victim of a phishing activity.Contacting paypal support and asking them to check the transactions and the IP can save his money.However,the money in paypal account might be chargedback from previous transactions if the "goods" option has been selected instead "service/other" so paypal may not be able to do anything about .t