Check for this please : 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.

Also check all your installed programs in Programs & Features for anything unknown and uninstall it, especially Toolbars.

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.

Also:

(1) Options Page Check

You can check for and remove unwanted search engine plugins on the Options page

• Windows: "3-bar" menu button (or Tools menu) > Options
• Mac: "3-bar" menu button (or Firefox menu) > Preferences
• Linux: "3-bar" menu button (or Edit menu) > Preferences
• Any system: type or paste about:preferences into the address bar and press Enter/Return to load it

In the left column, click "Search"

Then on the right side:

Default Search Engine

What shows here? You should be able to change this to Google or your preferred search engine (from among the installed ones, for others, you can try the Add-ons site).

If you changed this, does it stick -- or should I say, how long does it stick?

• Changed immediately on the next search
• Changed when you exit Firefox and start it up again
• Changes at a random time

One-Click Search Engines

If you see unwanted search engine plugins in this list, you can remove them. No need to remove built-in plugins like Wikipedia, you can just hide those by clicking the check mark in the left column ("un-check" them).

(2) Add-ons Page Check

Your default search engine -- the one Firefox uses when you search from the address bar -- can be changed by add-ons. You can view, disable, and often remove unwanted or unknown extensions on the Add-ons page. Either:

• Ctrl+Shift+a (Mac: Command+Shift+a)
• "3-bar" menu button (or Tools menu) > Add-ons
• type or paste about:addons in the address bar and press Enter/Return

In the left column of the Add-ons page, click Extensions.

Then cast a critical eye over the list on the right side. Any extensions Firefox installs for built-in features are hidden from this page, so everything listed here is your choice (and your responsibility) to manage. Anything suspicious or that you just do not remember installing or why? If in doubt, disable (or remove).

Any improvement?