Correct me if I'm wrong, but this doesn't look like this has anything to do with Syncthing vulnerabilities. Instead it looks like a hack that uses a preconfigured Syncthing installation to transfer sensitive data. Disturbing nonetheless.
It's a convenient file transfer/sync tool. Copying data has to happen somehow, I'm not surprised someone thought to use syncthing for that purpose >.<, since it can do that. But its not really different than any other tool here.