Seems like upvotes are mostly done with the users of this application, directly with the users' keys. Regarding the app accounts, here are the most common apps authorized amongst upvoters (2810)
[('busy.app', 1199),
('steemauto', 727),
('dtube.app', 688),
('steem.app', 615),
('dmania.app', 552),
('dlive.app', 530),
('bottracker.app', 441),
('steemhunt.com', 358),
('partiko-steemcon', 350),
('utopian.app', 289)]
This information itself doesn't point anything exactly, though. I was curious, here is the data for others also.
okay - the only one of those I use is SteemAuto. I just checked that one too (changing keys, etc, with SteemConnect as well...) I didn't have any unauthorized autovotes.