This was someone's attempt at a bitcoin public challenge: https://news.ycombinator.com/item?id=6765801 (Get a wallet's passphrase which was the username of someone in the Hacker News top 100, minus 2 characters).
Was amused to click through and see it was my username involved.
Mostly as I gave up ever trying to do anything with Bitcoin because I simply can't get my head around any of the practicalities, lol, so it definitely wasn't anything of mine! ;-)
I like that this was written in javascript. Was it meant to be injected onto webpages MITM-style?
The ID selectors would correspond to a form on a separate webpage, which the author is using jQuery to manipulate, so no injection.