What makes you think that Firefox is storing this data ?

Note that a detail like a website remembering you (log you in automatically) is stored in a cookie.
You can remove these special cookies to make the website forget about you.

Let the cookies expire when Firefox is closed to make them session cookies instead of using "Clear history when Firefox closes" to clear all cookies including cookies with an allow exception you may want to keep.

• Options/Preferences -> Privacy & Security
  Cookies and Site Data: [ ] "Delete cookies and site data when Firefox is closed"

You can create a cookie allow exception and use "Delete cookies and site data when Firefox is closed" to let cookies without allow exception expire when Firefox is closed

Hello Cor-el,

Thank you for your quick response. You have asked what made me think that Firefox was storing the data. There are two reasons why I thought Firefox might be storing the data and the cause of the change occurring in the behavior of Lastpass : 1. I have been using both Firefox and Lastpass for years now, and it was only after the last update to Firefox that the issue occurred. The icon to login to Lastpass appears adjacent my URL bar, and I have never thought of the login box as a "website." 2. Lastpass is very important to me, and it was very concerning to see my computer start and then automatically sign me in to Lastpass which it had never done before in Firefox or any of the other browsers I use, especially beacuse the Lastpass settings are configured to sign me out when I close the browser.

When I looked at stored passwards in Firefox, the menu said there were none saved which made me think my machine might have been attacked somehow. I figured I should ask the community. In any event, clearing the data and cookies resolved the issue regardless of what the change was within this version of Firefox.

Thanks much for your help.

Michael