Most applications for Windows support cutting or copying data to the Windows Clipboard and pasting data from the Clipboard. In most of the applications, only the most recent data is available for further usage. But internally, Windows Clipboard can save lots of data.
This data pose a serious privacy threat to the user. Imagine copying some important/personal data on the clipboard for pasting. But the data, after pasting, is still available with Windows Clipboard.

Windows Cleaner - CleanMantra effectively eliminates all the data on Windows Clipboard.