Hello annoyedatpopups,

This could be "a souvenir" from when all add-ons were disabled some days ago .....

If your extensions are (no longer) disabled; would you try to remove "hotfix-update-xpi-signing-intermediate-bug" from "about:studies"  ?

The only active study on that page is "prefflip-push-performance-1491171".

The fix I used for the disabled add-ons was by following the instructions on Hacker News that advised to download a file and install it rather than changing "about:studies" page.

Hello annoyedatpopups,

Using Firefox Sync will cause your master password to be requested upon starting the browser. When you click on the menu in the upper right-hand corner, does it show your email at the top?

Since this would be considered "logging in," the password request form generates.

You wrote "Firefox Send". Do you mean Firefox Send or is this about Firefox Sync? Sync stores the credentials to login to the account as JSON data in the Password Manager (chrome://FirefoxAccounts) and this requires to enter the MP when you start Firefox to be able to connect to the Firefox Account. There is no way to prevent this when you use Sync.

I signed up to *use* Firefox Send, but I guess the account is actually a Firefox Sync account.

After the pop-ups came a few times I looked up other people's solutions to the problem and I deleted my account. I also deleted the saved log-in username and password from "saved logins."

The menu in the upper right corner says "Sign in to Sync."

I don't want to use Sync, and while I liked Firefox Send it wasn't worth it for me to be asked for a password every time I open the browser.

A Firefox Account can be used for various services. I'm not using Send, so I do not know whether this service also wants to connect at startup.

• https://support.mozilla.org/en-US/kb/access-mozilla-services-firefox-account

I deleted my Firefox account before I posted this question and removed the stored log-in and password from "saved passwords" so it shouldn't want to connect as there are no credentials and no service to connect to.

Someone else mentioned "logins.json" but it does not have an entry for a Firefox account.

I am gaining access to this thread by responding from my email account, but I don't think that auto-login is causing the problem because it existed before I posted this thread.

Is there some other storage that may keep a copy of the deleted Firefox account credentials?

Another possible cause of the MP prompt at startup can be the hotfix extension to add the new intermediate certificate to the Firefox Certificate Manager. If you have this extension listed on the about:studies page then try to remove it when possible.

If you run Firefox 66.0.5 then you no longer need an extension or other workarounds to install the new certificate, so possibly also check the about:addons page.

Thanks, that sent me in the right direction.

Someone else had mentioned the about:studies page but the fix wasn't there as I had downloaded it and installed it with "Open File" so I checked my firefox/extensions folder and there it was: "hotfix-update-xpi-intermediate@mozilla.com.xpi".

Sorry for wasting everyone's time with my incorrect guess about the cause of the problem, and thanks again for the help.

annoyedatpopups said

Someone else had mentioned the about:studies page but the fix wasn't there as I had downloaded it and installed it with "Open File" so I checked my firefox/extensions folder and there it was: "hotfix-update-xpi-intermediate@mozilla.com.xpi".

That "someone else" would be me (see my first post).

I should have added to look for a hotfix related extension in Add-ons => Extensions - my bad (so sorry ,,,,).