Two mining pools largely control the Ravencoin mining, and have already begun rolling back the blockchain to a point prior to the invalid blocks. This is a controversial move in the crypto world, where immutability is considered sacrosanct. It's also disruptive, because legitimate transactions during that time period will be undone, with coins returned to the origin wallets. Several exchanges have halted RVN withdrawals and deposits, anticipating potential issues.
Ravencoin rolls back blockchain after exploit
Attackers exploited a vulnerability in Ravencoin, a blockchain based on the bitcoin codebase, to mine invalid blocks. Although Ravencoin subsequently patched the bug, the blockchain contains roughly four days of invalid history.