This isnt a "password trojan". All this addon does is add eventListeners to check for the modifier and alt-modifier keys, F1 to F10, insert and some others.

Once you press the hotkeys you set, the script will modify style.css to set all body and button colors to #222 or rgb34,34,34.

You can find all his stuff on his github (same name), hes pretty active.

3 stars because it breaks Thingiverse.com's thumbnails.