HI, This could be an issue caused by AdAware or Web Companion from Lavasoft. You can look for a file named dsengine.js in these locations. You should only find channel-prefs.js in the "defaults\pref" location. Any file found here apart from channel-prefs.js is suspicious. You can check the content of the file in a text editor (use open with and do not double-click the file). C:\Program Files\Mozilla Firefox\defaults\pref\ C:\Program Files (x86)\Mozilla Firefox\defaults\pref\ You can look for a file named dsengine.cfg in the main Firefox program folder. C:\Program Files\Mozilla Firefox\ C:\Program Files (x86)\Mozilla Firefox\ Delete the dsengine.js and dsengine.cfg files when present. Please use more than 1 scanner as each uses diff tech : *https://support.mozilla.org/en-US/kb/troubleshoot-firefox-issues-caused-malware Save your Report and google each before deleting anything as do not want to delete something you need, If need help : *https://forums.malwarebytes.com/topic/9573-im-infected-what-do-i-do-now/ Post in only 1 forum, then wait. Please let us know if this solved your issue or if need further assistance.