That program should be flashed on a digispark.
It uses UniquePasswordBuilder, which Firefox extension should be installed on your browser.
Project is described here : https://hackaday.io/project/167041-grandma-password-manager-helper When tapping the button, UniquePasswordBuilder is opened by shortcut, then master password is entered, validated and computed password is pasted on current field.
It helps using a password manager.
Beware : while it helps to use a unique and strong password for each site, that tool make it very easy to steal your master password.
Before compiling, copy password.h.dist into password.h and change the typed password inside.