hello, this sounds like a problem possibly caused by adware on your pc. #please go to the firefox ''menu ≡ > addons > extensions'' & remove any suspicious entries (toolbars, things that you have not installed intentionally, don't know what purpose they serve, etc). #also go to the windows control panel / programs and remove all toolbars or potentially unwanted software from there. #finally, run a full scan of your system with different security tools like the [https://www.malwarebytes.org/antimalware/ free version of malwarebytes] & [https://toolslib.net/downloads/viewdownload/1-adwcleaner/ adwcleaner], which are specialised in adware and browser hijackers. [[Remove a toolbar that has taken over your Firefox search or home page]] [[Troubleshoot Firefox issues caused by malware]]

Danke, es wurden keine Erweiterungen gefunden, aber "adwcleaner" hat offenbar etwas gefunden und entfernt!