BERLIN — Pan-European broadcasting group ProSiebenSat.1 continued its expansion into new media with the acquisition of a 25.1% stake in Autoplenum.de., a website aimed at auto fans.The broadcaster also has an option with German publishing group Georg von Holtzbrinck to up its stake in the site to 50.1%. The companies declined to provide financial details of the deal. The website was launched last year by Holtzbrinck eLAB and Malte Krueger, Autoplenum.de’s managing director. It will be added to the ProSiebenSat.1 Networld platform. Autoplenum.de consists of editorial test reports from various sources as well as users´ reports.