Has today’s Safari Security Update 2015-02 broken my Mac?

Since installing the update at lunchtime, my Mac has become almost unusable. Safari is freezing constantly, meaning I can use it for barely a minute at a time. I am experiencing severe keyboard input problems, with deletions, spaces and letters appearing randomly. Mail is behaving very erratically. When I tried to download the iMovie update, the login claimed my password was wrong: STATUS-CODE-ERROR. The fan is working overtime on my machine, suggesting that the problem is using up a huge amount of CPU.

I have only been able to post this by typing it up in Text Edit and then copy and pasting it into this field during a small window of Safari operability.

I am running OS10.10.2 on a 2011 MacBook Pro.

Anyone else suffering? This is catastrophic and Apple has to fix it ASAP.