Firefox opens a blank page by default, when the user opens a new tab, something installed on your PC changed that action to Bing.

See if this extension will override Bing and allow you to set your own choice of a web page for the new tab. NewTabURL extension:
https://addons.mozilla.org/firefox/2221/

This doesn't work either :(

Start Firefox in Use Troubleshoot Mode in Firefox to check if one of the extensions is causing the problem (switch to the DEFAULT theme: Firefox (Tools) > Add-ons > Appearance/Themes).

• Don't make any changes on the Safe mode start window.
• https://support.mozilla.com/kb/Safe+Mode

If it does work in Safe-mode then disable all extensions and then try to find which is causing it by enabling one at a time until the problem reappears.

• Use "Disable all add-ons" on the Safe mode start window to disable all extensions.
• Close and restart Firefox after each change via "File > Exit" (Mac: "Firefox > Quit"; Linux: "File > Quit")

• Troubleshoot extensions, themes and hardware acceleration issues to solve common Firefox problems

Is there a simple way to have a new tab open to a default website or does it require the add-on? It seems like this should be a standard option.

A new tab opens by default as a blank tab (about:blank).

You can middle-click or Ctrl left-click the Home button on the Navigation toolbar to open the Home page in a new tab.

You can look at one of these extensions:

• NewTabURL : https://addons.mozilla.org/firefox/addon/newtaburl/
• New Tab Homepage : https://addons.mozilla.org/firefox/addon/new-tab-homepage/

This fixed it. https://addons.mozilla.org/en-US/firefox/addon/new-tab-homepage/ Just set primary home page for Firefox to your search engine / website of choice and every new tab you manually open will open and pre-load that site. This will not override when you open another link in a new tab.

Cheers.