hello, this will be caused by malware which is active on your system, so 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 [https://www.malwarebytes.org/antimalware/ free version of malwarebytes] and [https://toolslib.net/downloads/viewdownload/1-adwcleaner/ adwcleaner] to make sure that adware isn't present in other places of your system as well. [[Troubleshoot Firefox issues caused by malware]]