Today's Quake 3 patch is brought to you by the letter P and the number 7. The latest version (1.17) fixes a serious security flaw in Quake 3 that allowed servers to overwrite any file on a player's computer! Ouch. The new version is, of course, not compatible with any previous version of Quake 3, so you'll have to download it if you want to play online.
For all of you out there using Linux or a Macintosh, head over here to find your own flavour of the patch.