When copying some content on a web page, it can happen that the clipboard contains more than what is visibly selected.
This is done for
- promotional reasons (e.g., an attribution line with link, appended, prepended or even injected somewhere inbetween),
- malicious reasons (see for example the proof of concept that you should never copy-paste from website to terminal),
- spam prevention reasons (e.g., for protecting an email address),
- etc.
In the 25C3 talk "Tricks: makes you smile" (demo), it was called WYSINWYC (What you see is not what you copy).
I’m looking for a Firefox solution (preferably an add-on), which must be FLOSS, that can notify/warn me somehow as soon as I have copied something invisible.
Because the hidden text can be injected via JavaScript, the warning should happen after copying (i.e., the content is in the clipboard), not after selecting.
(Some time ago, I suggested to include this in NoScript, but it’s probably not going to happen.)