Runescape account security?

Okay, so some noob sent me a video on YT, saying he's quitting RS, and hes giving away 1.3b+ cash. So being the dumb-*** I am I go to his fake ling, which is made to look like the RS forums. So I attempt to log in, and I didn't even check if it was actual runescape website. It took me three seconds to realize what I had done so I changed my password twice. What can he do with my old password, as that is the only information he has on me?