Hi Quechua, Firefox has three different field data storage features:

• Saved Logins - you've checked this one
• Form history - can be cleared as noted below
• Address filler - probably not relevant

You can clear the "Form & Search History" using the steps in the first section of this article: Clear recent searches from the Search bar.

If none of those have your saved logins, two other possibilities:

• The website recognizes you and prefills your user name -- sites do not prefill passwords
• An add-on or other external password manager is filling in the fields

You can view, disable, and often remove unwanted or unknown extensions on the Add-ons page. Either:

• Ctrl+Shift+a (Mac: Command+Shift+a)
• "3-bar" menu button (or Tools menu) > Add-ons
• type or paste about:addons in the address bar and press Enter/Return

In the left column of the Add-ons page, click Extensions.

Then cast a critical eye over the list on the right side. Any extensions Firefox installs for built-in features are hidden from this page, so everything listed here is your choice (and your responsibility) to manage. Anything that seems to be form or password related? If anything looks suspicious, or if you just do not remember installing it or why, please disable it for now.

Any progress?

You can also delete logins.json and formhistory.sqlite in the profile folder top remove all data stored in these files.

You can use the button on the "Help -> Troubleshooting Information" (about:support) page to go to the current Firefox profile folder or use the about:profiles page.

• Help -> Troubleshooting Information -> Profile Directory:
  Windows: Show Folder; Linux: Open Directory; Mac: Show in Finder
• http://kb.mozillazine.org/Profile_folder_-_Firefox