Double edit: the flag has been marked as helpful on August the 10th but nothing seems to have happened with the downvotes? I know it's just -2 rep for each downvote but it'd be great to see it returned :P
Edit: I've since flagged the user but the flag has been sat pending for some time. Hopefully it will be reviewed at some point instead of ageing away instead of sitting there pending for ages (thanks Shadow Wizard for the correction).
I've discovered a user that has admitted that they have used a script to downvote multiple answers on questions. Off this site they have posted a screenshot of the proof of the downvotes, and on the website where they posted it they have mocked people for calling them out.
I've cropped out the profile name for privacy.
I looked at some of the users on the answers that were downvoted and the votes have yet to be retracted.
Is there a way to report users like this? Their profile also seems to show some kind of annoyance against the moderation on the SE network.