I've seen the people who have had their posts show up under other poster's names. I would advise logging out and logging back in to see if it fixes the issue. If not, contact Rivals here and explain the issue: https://help.yahoo.com/kb/rivals?#/
I don't think anyone is hacked, I think Rivals has some internal issue.
I don't think anyone is hacked, I think Rivals has some internal issue.