I have finally updated to the latest version of Wordpress and detected several different spam attempts in my blog.
- The
index.phpandwp-content/index.phpfiles contained a couple of unwanted links (their size should be less than 100 bytes). - One of my posts had some invisible links added at its end. One to a chinese site, disguised with the
unescapeJavascript function and others hidden by setting the style todisplay: none.