Here is a command a site might offer you. It reads echo "test". Copy it, then
reveal what actually landed on your clipboard - here, or by pasting it into output-lies'
x-ray tool. It is perfectly safe to run:
every part is just echo.
echo "test"
You saw echo "test". Your clipboard held a whole second command chained on with
&& - echo "you did not expect this additional echo: unexpected code execution" -
kept to a single line on purpose. Paste multiple lines and several terminals warn you: we tested it, and
xfce4-terminal pops a "Warning: Potentially Unsafe Paste" dialog (its default, triggered by a newline in the paste), while qterminal offers a multiline-paste confirmation that is off by default.
One line joined by && trips neither - it slips in silently and runs the moment you press
Enter on a line you thought said only echo "test" (go ahead and run it - both halves are just
echo). The page only ever shows echo "test"; the Copy button's JavaScript quietly
writes the longer command to your clipboard instead, and slips a zero-width character in right at the
&& seam - it draws nothing, so a normal terminal shows no sign it is there. Real classes,
not hypotheticals: this is pastejacking, and the same paste channel carries
bracketed-paste bypass
and Trojan Source tricks.
secure-terminal strips the smuggling. A paste carrying any invisible, control or bidi
character is caught before it reaches your shell: secure-terminal names exactly what is hidden in it
("1 invisible character") and lets you drop it to plain ASCII or cancel - so nothing
rides along unseen and the text you are about to run is fully visible to read first. It cannot judge a visible
command for you - no terminal can, and a plain ASCII paste still submits; that is the opt-in
hook's job - but it guarantees there is nothing hidden inside the paste. The corpus's
adversarial harness
feeds every one of these payloads to secure-terminal and asserts it neutralises each one.