We just released Merit v0.5.5. It contains a critical bug fix that was identified and fixed overnight.
On the night of July 20th a failsafe in the Merit core software was triggered at block 296788. It prevented Merit Core from validating blocks and extending the blockchain. Consequently, this prevented the pools from working properly.
The blockchain stopped for approximately 6 hours because all the decentralized nodes detected a serious bug that caused invalid data to be propagated to the chain. We designed the software to stop accepting blocks in order to prevent bad data from entering the blockchain.
The Merit Foundation does not have a centralized way to stop the chain.
This design allows everyone in the Merit Community to be aware that there is a bug causing bad data, and allows everyone to potentially contribute to a solution. Of course, such occurences should be rare and engineers on the core team and in the community should address them with the utmost urgency. Which is what happened last night.
The problem that was detected was an overflow bug in the growth mining ambassador lottery. Immediately after discovering the problem we worked as fast as possible (overnight) to fix the bug and release a new version of the core software.
If you are running the LightWallet or Desktop LightWallet you don’t have to do anything.
If you are running the pool miners, the pool is working again and you should already be back in action.
If you are running the core software you can get a new version 0.5.5 with the fix here:
If you were running 0.5.4 or earlier and you had the “v.anv >=0” error, we recommend backing up your wallet.dat and removing the blockchain data. Then use fast sync to quickly catch up with other nodes.
If you are interested in seeing what caused the bug and its fix was in detail, you can look at these code changes on GitHub:
Going forward, we will be closely monitoring the blockchain and updating the community if any issues are discovered.