.malicious {
  color: #f3f5f6;
  position: absolute;
  left: -100px;
  top: -100px;
  height: 0px;
  z-index: -100;
  display: inline-block;
  -webkit-touch-callout: none;
     -khtml-user-select: none;
        -ms-user-select: none;
            user-select: none;
}


<code style="style=" background-color:="" #eeeeee;="" padding:="" 10px;"="">
<span>ls</span>
<span class="malicious">
echo 'Haha! You gave me access to your computer with sudo!';
<br> ls
</span>
<span>-lat </span>
</code>

You can fix it by binding Meta-v to a command that filters out \n from the clipboard (Bash4)

pasteline() {
  local input=$(xsel -b)
  input=${input//$'\n'}
  READLINE_LINE=${READLINE_LINE:0:$READLINE_POINT}$input${READLINE_LINE:$READLINE_POINT}
  READLINE_POINT=$((READLINE_POINT+${#input}))
}
bind -x '"\ev": pasteline'

Or write a command to safely paste code from the clipboard xcc $(command)

I said I had several functions, as there are several buffers, I name them like this:

function xcp() {
    if [[ -z "$1" ]] ; then
       echo $(xclip -o -selection primary)
    else
       echo -n "$@" |xclip -i -selection primary
    fi
}
function xcs() {
    if [[ -z "$1" ]] ; then
       echo $(xclip -o -selection secondary)
    else
       echo -n "$@" |xclip -i -selection secondary
    fi
}
function xcb() {
    if [[ -z "$1" ]] ; then
       echo $(xclip -o -selection buffer-cut)
    else
       echo -n "$@" |xclip -i -selection buffer-cut
    fi
}

can run as xcc or xcc $(command) to paste another commands output