Someone hacked me?

[ Moved to the Fixing WordPress sub-forum. ]

I’m trying to work out how someone hacked me to stop it from happening again.

I had one of my posts update 2 days ago to: “Hacked By XwoLfTn – Tunisian Hacker”

There was no author associated with the update, so I am guess it was through a plugin. The only plugins I have installed are:

– Facebook Comments Plugin by talspotim
– Google analytics by ShareThis
– Google XML sitemaps by Arne Branchhold
– Shareaholic by Shareaholic
– Simple Share Buttons Adder by Simple Share Buttons
– Yoast SEO by Team Yoast

I updated all the plugins just over 2 weeks ago before I went on holiday, and just came back to this. When I search for the same hack message in google, I get hundreds/thousands of other wordpress sites come up… but no info on how it happened or how to stop it.