Don't copy anything from a website to your terminal

Copy the following line:

touch note.txt && echo "some note" > note.txt

Copied. Now paste it somewhere.

It is possible that there is something in your clipboard that you do not expect.

A big problem is that some commands are executed immediately when they are inserted into a terminal.
The command you have on your clipboard now is fortunately only an echo.
When you paste it into terminal it is executed immediately:

Just imagine what could happen if the command has root privileges because you have already used sudo.

How you can protect yourself from it

Whenever you copy something, make sure you don't paste it immediately into your terminal
Paste it into a text file first, for example. Then you will see what you copied.

Update: An open-source browser extension is now available

The extension informs you whenever your copy action was hijacked by JavaScript

Check out https://github.com/roedesh/copyguard