OK, here's your scary discovery in online technology of the month. Well, at least it was a discovery for me.
(I'm assuming you will have already used copy and paste or cut and paste today. If not, copy something to your clipboard and then refresh the page.)
Yes, by the default settings, Internet Explorer can be made to paste the the contents of your clipboard into a web page. That's really special if you ever copy credit card numbers or passwords to your clipboard.
I would recommend changing your default settings in Internet Explorer:
Tools -> Internet Options -> Security -> Internet -> Custom Level -> Scripting -> Allow paste operations via script: set to Prompt or to Disable
Thanks to Dan Pinnington for passing along this tip from Rocky Stefano.
UPDATE: You probably want to choose Prompt rather than Disable above, if for no other reason than I have now discovered that the TinyURL application (that I love and use frequently) uses this as a part of its process. So better to be prompted for this, or something else, than to have it suddenly stop working.