Hi   !

Go to the 3-bar menu => Addons => and look for any unfamiliar or suspicious looking extensions, like e.g.:

SafeSearch Incognito SearchAssist Incognito

When you find any :   remove them.

Also look in :   Advanced => Network tab => Under : 'Offline Web Content and User Data'

Do the same in Windows' Control Panel => Programs.

However :   most malware will be 'hiding' somewhere , so, even if you already have run malware scans :

Would you please take a look at this article :
https://support.mozilla.org/en-US/kb/troubleshoot-firefox-issues-caused-malware?cache=no

Run most or all of the listed malware scanners.
They all work differently   -   what one program doesn't pick up, the other might.

Also see : https://malwaretips.com/blogs/activities-aliexpress-com-removal/

Unfortunately this did not solve the problem. HitmanPro found a couple things but didn't fix this one.

Any other suggestions?

CarlT said

Unfortunately this did not solve the problem. HitmanPro found a couple things but didn't fix this one. Any other suggestions?

Did you look for unfamilar or suspicious looking software and scan with   all   malware scans   ? (Do not use 'Zemana', though)

Do you have any add-ons, and if so : which ones  ?

You could consider installing uBlockOrigin :

https://addons.mozilla.org/en-US/firefox/addon/ublock-origin/

And also check these settings :

3-bar menu => Options => Security => under 'General' : Make sure all four boxes are checked.

Did you try Malwarebytes' Anti-Malware?

• http://www.malwarebytes.org/mbam.php