There's a strange cookie with a long hexadecimal name that keeps showing up in my CCleaner cookies list (see image).
The cookie shows up a few seconds after I launch Firefox, even before I visit any sites. When I run CCleaner, the cookie goes away, but it comes back again the next time I launch Firefox. CCleaner shows the Firefox icon at the bottom of the cookie windows, but, oddly, the cookie does not appear in the cookies list in Firefox settings.
What is this strange cookie, and how do I make it go away?