He can’t even vote yet. The plug-in is called Greenhouse, and it works similarly to the “reveal codes” function.
“After installing the plugin on Chrome, Safari, or Firefox, Greenhouse will highlight the names of any members of Congress no matter what webpage you’re on. When you hover your mouse of the highlighted name, a list pops up showing the elected official, their political affiliation and state, and a full list of their biggest contributors, as well as dollar amounts. The pop-up also shows what percentage of the official’s donations were $200 or less, and which campaign finance measures they supported.” –The Daily Dot