Unrestricted file upload vulnerability in (1) wp-app.php and (2) app.php in WordPress 2.2.1 and WordPress MU 1.2.3 allows remote authenticated users to upload and execute arbitrary PHP code via unspecified vectors, possibly related to the wp_postmeta table and the use of custom fields in normal (non-attachment) posts.  NOTE: this issue reportedly exists because of an incomplete fix for CVE-2007-3543.