Ravencoin, a blockchain built from Bitcoin’s code, could roll back four days of transactions

The consequence is simpler for a user. A payment that looked complete over the weekend could vanish from Ravencoin’s record, with the coins returning to whoever sent them and the recipient left with nothing.

The exposure sits with anyone who gave something up on the strength of a payment that no longer exists. An exchange that credited a deposit and allowed the customer to withdraw against it would be left short, which is why several have stopped taking RVN in at all.

Amsterdam-based Bitvavo suspended RVN deposits and withdrawals as a precaution, citing the exploited vulnerability. South Korea’s Upbit placed an investment warning on RVN across its won, bitcoin and tether markets and also stopped deposits.

What happened

The first bad block appeared at height 4,487,776 at 15:44 UTC on Aug. 7. Once the weakness had been demonstrated on the live network, others appeared to copy it and produce invalid blocks of their own. Ravencoin has since released a fix, but patching the software does not undo what is already written.

The two pools, 2Miners and RavenMiner, are building their version from block 4,487,775, the last one before the exploit. The project said it asked them to restart from a more recent point, which would put less history at risk, but they declined.