Logins spreadsheet created and saved to desktop automatically.

You can check that pages aren't set as multiple homepages. Firefox supports multiple homepages separated by '|' (pipe) symbols. You can check the homepage setting in "Settings -> Home". *https://support.mozilla.org/en-US/kb/how-to-set-the-home-page

Firefox doesn't create such a Logins.csv file by itself as this will require confirmation (authentication), so if you get this file 0n the desktop each time you boot the computer even when Firefox isn't running then it must be coming from somewhere. Boot the computer in Windows Safe Mode with network support to see if that has effect. *[https://www.bleepingcomputer.com/tutorials/how-to-start-windows-in-safe-mode/] *[https://www.digitalcitizen.life/4-ways-boot-safe-mode-windows-10/] You can do a malware scan just to be sure. *https://support.mozilla.org/en-US/kb/troubleshoot-firefox-issues-caused-malware