For Apple OS X users only:
Yesterday I got 3 OS X updates, they were labeled as Thunderbolt updates/fixes as I recall. Along the way I think Safari (OS X default browser for any non-apple folks reading this far) got an update. I found that many of my Safari extensions “magically” got deactivated with no warning. Not Good! AdBlock, Ghostery (a great anti-spyware/tracking extension, recommended!), Readability, Google Disconnect, Facebook Disconnect, Twitter Disconnect (the last 3 block much of the spying/tracking activities of these companies) were deactivated without my consent. And my default search engine was switched from GoDuckGo (a non-tracking search engine, works well most of the time) to Google.
If you recently got some OS X updates, check your Safari extensions.