From now on auction owner can change quantity, "Now price" and Add time to auction. For more details see "Change Auction Data" (http://www.l2.mog.tc/faq#auctionedit).
that's not a keylogger, for 100% that user are safe we strongly advice not to use the same login and password as you have for your account in the game.
This site is a means to organize in-game auctions, sales, and purchases so you don't have to spend your time in-game doing so. Think of it as a tool. You don't actually make any sort of exchanges out of the game (that sort of thing would be illegal).
something like this exists for diablo2 since a few years. I personally thinks it's a cool idea and i hope that at least a few people will join.
It's pretty hard to sell weapons or other stuff on my server since the server transfers became available. This site COULD help ;)