hello noelware, can you try to replicate this behaviour when you launch firefox in safe mode once? if not, maybe an addon is interfering here...

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

I restarted in Safe Mode and the behaior is the same. The same thing happened when I came to this support site. https://support.mozilla.org Up came the password manager window. I closed the password manager window without entering anything and the site works fine. Strange...

Are you using Firefox Sync?

Create a new profile as a test to check if your current profile is causing the problem.

See "Creating a profile":

• https://support.mozilla.org/kb/profile-manager-create-and-remove-firefox-profiles
• http://kb.mozillazine.org/Standard_diagnostic_-_Firefox#Profile_issues

If the new profile works then you can transfer files from a previously used profile to the new profile, but be cautious not to copy corrupted files to avoid carrying over problems.

• http://kb.mozillazine.org/Transferring_data_to_a_new_profile_-_Firefox

I have been using the password manager for some time.

But... No, I haven't used Firefox Sync as I didn't see a need for it. (One PC...)

I see in the links about profile management, there is mention of a "Reset Firefox" feature. Seems like a strange requirement to have to reset a browser.?

Do you think "Reset" might help? (Some Deja Vu here. Its starting to sound ike Microsft)

Seeing the mention of addons possibly being the cause of the password manager window popping up, I disabled all Firefox addons. But the window still pops up, but not instantly. Tonight it popped up twice. Once while while using Google and once using eBay. Both times there was nothing happening which required a password.

This has only started to happen since the last Firefox update, (34.0.5)

Perhaps the update has changed something...?

i haven't seen any change after the update (or reports from other people with the same issue)... what you might also want to try is to run a full scan of your system with multiple security toolslike the free version of malwarebytes and adwcleaner.

Try disabling these add-ons;

Saved Password Editor 2.8.1 Show my Password 2.0 Show/hide passwords 0.3

BTW, do the last two do the same thing?

FredMcD Thanks for the suggestion. I have those add-ons installed, but all my add-ons are disabled. Prior to disabling all add-ons, the Password Manager window was popping up on every google search. After disabling its happened a couple of times. I'll leave all the add-ons disabled for a while and see how it goes.

Philipp I have Bitdefender free edition installed. So I'm reasonably confident the system is virus free. Even so, I'll try those cleaners.

Thanks for the responses