hello jan, please go to ''firefox > addons > extensions'' & remove the ''Addons Engine 3.0.1 & DataMask by AOL 5.6.0.8734'' entries (they are rather unusual and are likely malicious). also go to the windows control panel / programs and remove all toolbars or potentially unwanted software from there and run a full scan of your system with different other security tools like the [http://www.malwarebytes.org/products/malwarebytes_free free version of malwarebytes] & [http://www.bleepingcomputer.com/download/adwcleaner/ adwcleaner]. [[Remove a toolbar that has taken over your Firefox search or home page]] [[Troubleshoot Firefox issues caused by malware]]