Just found this segnalation about a possible side effects (or flaw) of Internet Explorer (with or without XP SP2).
It seems that if you place a special Javascript code on a page, with IE you can extract data out of user's clipboard and modify it or post the content on the server. Not good... 
You can try it by yourself, just click the link below:
Show clipboard contents
You can stop the problem by taking these actions:
Go to Tools --> Internet Options... Click on the Security Tab Select Internet Zone and then click Custom Level... Scroll down to the scripting section and see "Paste operations via script" Change the value to Prompt or DisableP.S. Firefox is not affected by this problem.