Search online for how to remove your malware infections.

First step: Restart in Firefox's Troubleshoot Mode

In that mode, Firefox temporarily deactivates extensions so they cannot interfere with use of built-in features.

If Firefox is running:

You can restart Firefox in Troubleshoot Mode using either:

• "3-bar" menu button > Help > Troubleshoot Mode...
• (menu bar) Help menu > Troubleshoot Mode...

and OK the restart. A small dialog should appear. Click the Open button.

If Firefox is not running:

Hold down the option/alt key when starting Firefox. (On Windows, hold down the Shift key instead of the option/alt key.) A small dialog should appear. Click the Open button.

Note: Don't use the Refresh without first reviewing this article to understand what will be deleted: Refresh Firefox - reset add-ons and settings.

Second step: Extension Clean-up

You can view, disable, and often remove unwanted or unknown extensions on the Add-ons page. Either:

• Command+Shift+a (Windows: Ctrl+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.

Before restarting...

Third step: Settings clean-up

The intruder might have modified your home page, new tab page, default search engine, or other settings. Here are some articles for these:

• How to set the home page
• An extension changed my New Tab page or home page
• Change your default search settings in Firefox

Finally, quit Firefox and start it back up again normally. Success?

Thanks for your help but nothing has worked. After using Firefox for 20 years, I'm going to have to switch browsers. It's a shame that the Mozilla corporation isn't aware of this problem and can't suggest an immediate remedy.

Where does it still appear?

If it's a bookmark on your Bookmarks Toolbar, right-click (or Ctrl+click) and Delete Bookmark.

If its hooks are in deeper, try a Refresh. See: Refresh Firefox - reset add-ons and settings.

I tried to refresh and it didn't work. I even deleted Firefox completely, re-downloaded it, and was still looking at my quick converter.

It is sounding more like an external infection. You could try:

https://www.malwarebytes.com/mac

I have been running Malwarebytes for over three years, and obviously didn’t help.

I don't understand where My Quick Converter is at this point. You cleaned:

• Extensions
• Home page setting
• New tab page setting
• Default search engine setting

What triggered it to return -- was it when you quit and restarted Firefox -- and where did it return to?