Couldn't find an translation of this report, so here is the link to the German version: http://www.spiegel.de/netzwelt/web/web-of-trust-browser-add-on-spioniert-angeblich-nutzer-aus-a-1119236.html
Here is the gist of the article: WOT collects and sells user data to third parties that is not sufficiently anonymized, thus allowing to identify individuals and making them susceptible to blackmail.