A Moment Of First World Terror

I clicked "install update" for my copy of Mozilla Thunderbird.

It did it's thing and when it restarted, it informed me that it required OSX 10.9.

I am still running 10.6.8.

Happily, Mozilla still has a dmg I can download and install that fixes the problem.

Sadly, they don't have their installer check compatibility with the OS version before installing.