hi, plase try a clean reinstallation: * uninstall firefox from the system control panel * manually delete all remaining files in the firefox program folder afterwards - it usually resides in ''C:\Program Files (x86)\Mozilla Firefox\'' * download & reinstall firefox from https://www.mozilla.org/en-US/firefox/all/ finally, please 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] as this might be a symptom of malware on a machine, unless your device is part of a managed enterprise network where such central configurations might be used...