With Firefox on X11, any page can pastejack you anytime (middle button paste)
The X “primary selection”/middle click paste behavior this takes advantage of is one of my least favorite Linux features and I have had it disabled for years, so I didn’t even know it had been changed/removed in Wayland.Having a single mouse button (that often has other functionality like autoscroll in Firefox) cause text highlighted in another app to paste in the focused app is super unintuitive to me, and caused a few significant annoyances unintentionally pasting  secrets or private messages in the wrong place before I got rid of it.