It looks like there is some unknown exploit that is being used to hack into WordPress sites en-mass.
The following threads and sites will tell you more about it and how you can find out if you are effected.

http://wordpress.org/support/topic/385477

http://techcocktail.com/home/2010/04...earch-engines/

Note: third link removed - - see post #2
update: seems this site was itself hacked - the author believes it is clean now the site is www christopherspenn com/2010/04/07/find-the-latest-wordpress-hack/

http://www.themelab.com/2010/03/01/d...earch-engines/

BEWARE - Third link in list attempted to install a Trojan Horse when I visited the site.

Ok, I went through all the information, but I am really techno challenged here. First of all is there an easy way to see if one or more of my sites are affected? I am checking at the moment my page source for the homepage of all my sites, is that enough? Any help appreciated! SY

Seek The Truth - what were the symptoms?
What browser were you using?
What OS?
I don't have a problem, but I'm using a mac...

I read somewhere that you can Google your site, and if the page that comes up has a bunch of links to other sites, you've been hacked.

.Hey...

Same thing as Seek the Truth said - third link attempted to install malware upon visiting - I'd remove the link.

M.

I made the security changes we discussed a short while ago, JD. Will those prevent what's happening here, or should I look further into this?

Thanks.

Velma

Velma, I'd look into this also

My site was hacked a couple of years ago - in fact is was so bad it was totally destroyed. Google sent me loads of warning messages and blocked my site from their search. All very embarassing. I just hope by keeping the software up to date I'm secure from this sort of thing now I've relaunched my site.

Tom

Interesting update on the Wordpress blog http://wordpress.org/development/201...e-permissions/
Seems it was hosting specific ;-( SY