I posted this question A question involving dead cats several months ago, and it received one upvote around that time.
It was last edited several months ago, and any vote should be locked in after 5 minutes after the vote was cast, unless the post is edited.
So the upvote shouldn't be able to be undone, and yet recently it was unupvoted.
I don't care about the reputation loss, I am just curious, how can this happen? Did someone hack the system?