I believe the security risk is primarily sniffing the clipboard continuously when you expose a tab (or in horrible implementations, have a tab open). Use a pas

I believe the security risk is primarily sniffing the clipboard continuously when you expose a tab (or in horrible implementations, have a tab open). Use a password manager that puts the password into the clipboard, flip past the hostile tab, the site now has one of your passwords. Copy a big chunk of text from a sensitive email or document, now they've got that as well. Secret urls, auth tokens in urls, private email addresses? Same. Putting something into your clipboard is kind of annoying and could be a small security risk, but pulling the contents out is much worse. If it's a site you don't visit often it would be limited exposure, but if someone manages to hack Soundcloud/Pandora or inject JS into them you're talking about a lot of illicitly acquired information. Most of it may be useless, but it's a sucker-bet to assume no-one will get hurt by it.