Hi florus,

My first suspicion is that an Add-on is behind this.

You might want to check your Add-ons against the Blocked Add-on List here:

https://blocked.cdn.mozilla.net/

Are these cookies or storage items?

See also:

• https://developer.mozilla.org/en-US/Tools/Storage_Inspector

If clearing cookies didn't help then It is possible that the cookies.sqlite file in the Firefox profile folder that stores the cookies got corrupted.

• rename/remove cookies.sqlite (cookies.sqlite.old) and when present delete cookies.sqlite-shm and cookies.sqlite-wal in the Firefox profile folder with Firefox closed in case cookies.sqlite got corrupted.

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

Many thanks for your help. It does not seem to be related to my add-ons so deleting the three cookies.sqlite files will be the best solution. I may be over reacting, but I dislike unexplained files or other entities on my computer.

cor-el,

Thank you. Your suggestion to delete the cookies.sqlite file using %APPDATA%\Mozilla\Firefox\Profiles did the trick.

Like florus, I am a bit paranoid about not being able to delete cookies in the section Manage Data that do not have a name. They are gone now, so thanks again.