Otilia

Having the very same problem, after the most recent update (yesterday):

– received the following Warning: Invalid argument supplied for foreach() in /home/…/wp-content/plugins/jetpack/jetpack.php on line 4527

after deactivating and re-activating, I receive the same error (taking the site down) with the following notification: “The plugin generated 183 characters of unexpected output during activation. If you notice “headers already sent” messages, problems with syndication feeds or other issues, try deactivating or removing this plugin.”

I’ve also had 3 sites hacked the very same way – earlier today. The only changes I was able to see were:

– change of site title (Settings -> General)
– change of encoding to UTF-7, resulting in some scrambled text.

This is, fortunately, not a big deal to fix. However, a quick search shows this threat is spreading out very very fast! In fact, a second site of mine was hacked just as I was fixing the first one.

It is surely worth having a look and start collecting data?

[later edit] – The intention I’ve had with this reply was to add more information to what the original poster mentioned and to confirm it was not a singular occurrence. I had not asked for any help or input whatsoever and have not diverted attention from the initial issue reported here.

Donncha,

thanks for such a super-fast reply! ??

I’ll look it up and post back here.

Cheers,
Otilia