Try this:

Once you open Mozilla Firefox browser, go to the Tools section.

Now move to the Add-ons and go to Extensions.

Here you should look through the list, find key-find.com and just simply uninstall it.

After that, you must go to the Tools section again and choose Options.

Here you have to go to the General section and finally select Startup.

Final step is to set a particular website or just simply an option ‘show a blank page’.

If key-find comes back, there may be malware on your computer that will keep pushing it into Firefox.

I suggest going into the Windows Control Panel, Uninstall a Program, and clicking the "Installed on" column heading to bring the most recent infections, er, additions, to the top. This also groups by date so you can see and remove unexpected bundled programs.

When I search online for remove key-find there are many, many different "carriers" mentioned so I suggest removing everything recently installed that does not sound essential.

After that, you may want to use some of the scanners listed in this article to mop up any remaining items: Troubleshoot Firefox issues caused by malware.

Hope this helps.

Oh, one article also mentioned a possible hijack of your program shortcuts. To check that:

right-click the icon you use to start Firefox > Properties > Shortcut tab

On 64-bit Windows 7, the "Target" line should have the following, no more, no less:

"C:\Program Files (x86)\Mozilla Firefox\firefox.exe"

First of all, my recommendation is that you perform the removal of this Key Find hijack manually. Scanning with anti-virus programs will not help you anyway, because not all of them detect this Key Find as a virus. Not even as malware. I found how to remove Key Find from this article But you need to go down to the page where it contains the instructions for Mozilla Firefox browser specifically. These are all manual steps, and I hope that this will help you.

Additional info

Please take care when reading instructions on other websites.

Instructions from system-tips.net mainly seem reasonable and useful however they often include a step involving their paid for software.

There are nearly always alternative methods of completing such steps either with free software or simple manual steps.

Sites offering free advice as listed in

• Troubleshoot Firefox issues caused by malware
  • Bleeping Computer Forums
  • Spyware Warrior Forums
  • SWI Forums

And (for Windows OS) tools listed from the above article.

• Malwarebytes' Anti-Malware Free
• SuperAntispyware Portable Scanner
• Microsoft Safety Scanner see https://www.microsoft.com/security/pc-security/malware-removal.aspx
• Anti-Rootkit Utility - TDSSKiller
• AdwCleaner (see this alternate AdwCleaner download page for more information)

Ensure the tools are up to date, and use them all, as no single appliction catches everything, and once malware or adware has been present for any length of time there are often multiple issues.

You have to uninstall those suspicious software or add-ons from your computer and Firefox before changing back your home page and search engine. Otherwise, those malicious stuff can keep changing your browser settings.