- On locked screen, draw an incorrect pattern 5 times till the button 'Forgot pattern?' appears.
- Click on this button.
- Click on the text box where the blinking caret is in order to make the text selector appear (you may need to click twice).
- Click on the text selector.
- And then click on 'Clipboard'.
You can then see all the clipboard history of the user...!
As far as I know, this hack is only working on Samsung Devices.