You may have ad/mal-ware. Further information can be found in 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. Each works differently. If one program misses something, another may pick it up.

Remove History For One Site {web link}

Open the History Manager <Control> (Mac=<Command>) <Shift> H. In the search bar, enter the name of the site. Right-click on one of the listings and select Forget About This Site. This should remove all information, including any site settings

Malwarebytes

Website blocked due to a Trojan

Your Malwarebytes Premium blocked this website because it may contain a Trojan.

We strongly recommend you do not continue.

Here's the message I get: Attacker URL icelandsue.com/metric/?

The attack was resulted from DEVICE\HARDDISKVOLUME3\PROGRAM FILES\MOZILLA FIREFOX\FIREFOX.EXE.

System infected: Malicious Browser extension Activity 10

I'm not using icelandsue.com it's just everytime I try to go into any website I get that message.

I've tried all the suggested prevention methods but still have the issue.

System infected: Malicious Browser extension Activity 10

You can view, disable, and often remove 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. On the right side, find the "Manage Your Extensions" heading.

If there is at least one extension before the next heading -- "Recommended Extensions" -- please continue:

Then cast a critical eye over the list below that heading. 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). For your privacy and security, don't let mystery programs linger here.

Any improvement?