hello, it looks like there are some malicious modifications present in firefox that didn't get detected by your anit-virus software. please perform all these steps: # [[Reset Firefox – easily fix most problems|reset firefox]] (this will keep your bookmarks and passwords) # afterwards go to the firefox menu ≡ > addons > extensions and in case there are still extensions listed there, disable them. # finally run a full scan of your system with different security tools like the [http://www.malwarebytes.org/products/malwarebytes_free free version of malwarebytes] and [http://www.bleepingcomputer.com/download/adwcleaner/ adwcleaner] to make sure that adware isn't present in other places of your system as well. [[Troubleshoot Firefox issues caused by malware]]

The procedure suggested by Philipp did not solve this problem. Please recommend another solution.