The only way to do this is either disable the Password Manager or create a block exception for these websites. With a block exception Firefox won't ask to save or update a password.

HI, please Copy/Paste about:preferences#privacy to the Address Bar then Enter. Under Notifications Click on Settings then put a tick in the box at the bottom. Also put a check mark in block pop-ups. When go to a site and it offers up that there should be a a allow and Never ask Again. Please look for that next time. Also the in the Address Bar there is the site Information with a i on a circle click on that then the arrow > , then More information then Permissions and change permissions. If no Never Ask again please do this : uninstall Firefox. Then Delete the Mozilla Firefox Folders in C:\Program Files , C:\Program Files(x86) & C:\ProgramData Then restart system. Then run Windows Disk Cleanup. (Note: This should be Pinned and run Weekly, If never done below expect 10's of gig's) Then run it again and click the button that says Cleanup System Files. Note: your Firefox Profile is saved. But you should make a back up before you do : *https://support.mozilla.org/en-US/kb/back-and-restore-information-firefox-profiles *https://support.mozilla.org/en-US/kb/export-firefox-bookmarks-to-backup-or-transfer Reinstall with Current Release Firefox 60.0.2 with a Full Version Installer *https://www.mozilla.org/firefox/all/ Please let us know if this solved your issue or if need further assistance.