[treesprite82]

Default behavior being for a single mouse button to paste and run (if it contains newlines) whatever's on the clipboard always seems dangerous to me. Beyond the accidental mistakes, I bet a website could catch a lot of people out about not checking in a text editor if it presented an innocuous command then swapped it out (with JS or tiny invisible text) for something nefarious when copied.

[mjw1007]

Many (most?) combinations of a terminal emulator and a shell nowadays won't run pasted content without a further press of the return key.

This is a consequence of "bracketed-paste mode".