Update 2012Oct12: Version 16.0.1 of Firefox has just been released. The new version fixes the vulnerability that caused version 16.0 to be pulled from the Firefox download site yesterday. All users are encouraged to upgrade to 16.0.1 as soon as possible.

Firefox 16.0 has been removed from the Mozilla web site due to a new vulnerability. Users who have already upgraded to the new version should either downgrade to version 15.0.1 or exercise extreme caution before visiting any unfamiliar or suspicious web site. The new vulnerability makes it possible for web sites to access information that is normally protected by the browser.

Update 2012Oct12: No exploits using this vulnerability have yet been seen in the wild, but a proof of concept has been published. The POC demonstrates the vulnerability with a few lines of Javascript code that could be embedded on a web site. Now that this POC has been made public, it’s reasonable to assume that similar code will start appearing on hacked and malicious web sites in the very near future.