"Earlier today the WordPress team noticed suspicious commits to several popular plugins (AddThis, WPtouch, and W3 Total Cache) containing cleverly disguised backdoors," explained Matt Mullenweg. "We determined the commits were not from the authors, rolled them back, pushed updates to the plugins, and shut down access to the plugin repository while we looked for anything else unsavory."
If you use the WordPress platform and have updated one of these plugins in the past two days, you are at risk. You have to upgrade them again - WordPress has pushed out their new, safe versions.
Also, if you have an account on WordPress.org, bbPress.org and/or BuddyPress.org, don't be surprised to find a reset password message the next time you login into your account.