Just had this reported on one of our sites.
There was spam link injection in the footer that came from a php file uploaded to wp-content/uploads/2009/01 called fonction.php and wp-links.php (These are base64 encoded, haven’t looked at them yet)
The blog is running 2.7.1
Installed Plugins:
Akismet 2.2.4
All in One SEO Pack 1.5.7
Category Replacement Widget 0.5
Get-a-Post R1.4
Homepage recent entry 1.0
MailPress 1.9.1
Secure and Accessible PHP Contact Form v.2.0WP B20080731
Sticky Menu 1.41
wp-Table 1.52
WP Shopping Cart 3.6.8 RC1