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 also search and Check Programs and Features for Web Companion in the list and uninstall it before doing the above.

Please give your self a scan also : https://www.malwarebytes.com/

Is there a reason you have 2 different versions of iMacros installed and active ?

Please let us know if this solved your issue or if need further assistance.

Thanks for your quick response. Tried your suggestions. No dsengine.cfg or dsengine.js files anywhere on my computer. No Web Companion either. Very strange and frustrating problem.

I have two versions of iMacro because I'm trying to get the newer version to work in FFox 56. I deleted the newer version earlier today, but still had the hijacking problem so I re-installed it.

Hi, Welcome. If meaning reinstalled Firefox reinstall may not work. Please use Malwarebytes to make sure your clean.

Running Malwarebytes eliminated the problem. Thanks for your advice but I'd still love to know how this crap gets into my computer.