Hmm, that is supposed to be dropped from the $_POST variables before it gets to the scripts.

Try this, at line 169 of admin/doupdatestyle.php you'll see this:

PHP Code

if (preg_match("/(returntab|style|style_name|news_images|general_images|avatar_images|forum_images|markup_images|graemlin_images|icon_images|wrapper|mood_images)/",$key)) continue;

Add valid_post to that list of checks, so change that to this:

PHP Code

if (preg_match("/(returntab|style|style_name|news_images|general_images|avatar_images|forum_images|markup_images|graemlin_images|icon_images|wrapper|mood_images|valid_post)/",$key)) continue;