Thanks Mike and others for digging in to the security fixes and changes in the recent Firefox 16 and Thunderbird 16 updates (earlier this week).  Find these details here:

https://www.mozilla.org/security/known-vulnerabilities/firefox.html

https://www.mozilla.org/security/known-vulnerabilities/thunderbird.html

.. And thanks to our reader Paul, who let us know that this latest update has been pulled (if you download the lastest version right now, it's 15.0.1).  It seems that a critical security vulnerability slipped past in 16.0.  (version 15.0.1 is not affected).  Good on the Firefox / Mozilla teams for pulling it so quickly, and posting on it immediately.   More info here:

https://blog.mozilla.org/security/2012/10/10/security-vulnerability-in-firefox-16/

Final Update (we hope):

Another reader has just let us know that 16.01 has just been posted - this should get us all back on track!  Happy updating everyone!  The two original links (above) have the security-specific info for version 16.01

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Rob VandenBrink
Metafore