I received a mail from my web hosting asking me to upgrade my wordpress version if I’m using WordPress 2.1.1. It appears that a hacker had gained user-level access to one of the servers that powers wordpress.org, and had used that access to modify the download file.
Although not all downloads of 2.1.1 were affected, WordPress team are declaring the entire version dangerous and have released a new version 2.1.2 that includes minor updates and entirely verified files. So update immediately if you are using version 2.1.1. Hopefully this will not happen again. Damn hackers!~