On December 15th 2014, the Opal team officially announced a malicious wallet attack on Opal users. Approximately 2.5 Million Opal coins were stolen, equivalent to about 17% of the total supply. A rollback was voted on by the community, but after 65% of the coins were returned, the Rollback was canceled.

Soon after, the hacker got in contact with the Opal team and negotiations lead of 65% of the funds being returned to the Opal team, which will be returned to their rightful owners proportionally. The funds have been transferred to the Opal team and as a result the rollback has been canceled.

Before negotiations took place, the hacker would have held too large a portion of Opal which could have threatened the decentralization of the blockchain. Thanks to 65% of the coins being returned, the Opal Team believes this danger has been averted and a rollback would have set a bad precedent, and thus is not justifiable.