Some over time have developed quite the collection of these files, taking up GB's of space. Firefox did this too on mine, taking room for cumulative Crash Reports over time, which I disabled to avoid it anymore.
Happens in Tor Browser too.
Fixed in 2010? Nope.
Just remember to find and check /tmp or /temp folders from time to time, not just for abandoned clipboardcache files, but other files abandoned there too.
Heads up on an old problem that still persists, both in Linux and Windows when using Firefox browser. In Linux Firefox creates these clipboardcache files with a number up for anything entered to cache over 1MB in size. Used to be anything over half a MB in size. Firefox doesn't remove them all and they build up, taking up space. These are found in the /tmp folder, not sure exactly where placed for Windows computers, probably /tmp or /temp.
Seems the only solution is to find them manually and delete them. For windows computers just use Search and enter the filename without any number "clipboardcache" and search all drives.
Here's a screen capture of them on my Mint Linux 17 version.