This has been a "bug" for a long time with exactly the same behavior that is described here. Copy&paste from a news article or a blog and have something like "r

This has been a "bug" for a long time with exactly the same behavior that is described here. Copy&paste from a news article or a blog and have something like "read more at <URL>" inserted. It's also not Firefox-specific. Same behavior happens in Safari and Chrome. But yeah, it makes total sense to point this out that hijacking the clipboard is probably not a good idea and this might be a security issue.