I don't see why this is getting downvoted. Traditionally Google does make corrections after a significant update. The website in question is still receiving traffic and isn't completely out of the index, and could very well see the rankings go back in a week or two.
If you panic and start making site changes immediately, you may not know what the cause of the problem was. If you go and change title tags, remove some spammy looking links, change the anchor text and a handful of other things you would not know which was effective and which wasn't.
It's like pulling your goalie in hockey after going down 2-0 in the first 5 minutes. Let the updates play themselves out for a week or two and go from there.