Hi all,

The Monero network was (once again) the subject of an attack. Due to an error during the development of 0.9, Hydrogen Helix, we omitted a check that allowed for v2 blocks to be added to the network prior to the hard fork block height. Thus instead of forking on March 20, at block height 1009827, a v2 block was added to the network at block height 913193.

This is obviously problematic as not all services have updated to 0.9, and the bulk of the network hash rate is still on 0.8.x. We are preparing a point release to 0.9 that resolves this, but in the meantime only if you are running 0.9 you can do the following as a quick patch:

1. Shut down your Monero daemon
2. Grab a checkpoints.json file from getmonero: https://downloads.getmonero.org/checkpoints.json
3. Put the file in your bitmonero working directory (eg. ~/.bitmonero or C:\ProgramData\bitmonero)
4. Restart the daemon

As soon as the patched point release is out you can remove the checkpoints.json file, if you wish, and run the updated version. The checkpoints.json patch is a quick fix and does not prevent the attacker from replaying their attack at a later block.

Update, 2016-01-15, 18:15 UTC

0.9.1 has been released, which patches this. You can upgrade directly to 0.9.1 without doing anything else, and if you are on the wrong fork it will reorganise the blockchain for you.

Release Page: https://github.com/monero-project/bitmonero/releases/tag/v0.9.1

Download Links

• Windows, 64-bit (Hash: 303840d7fb997b2f1efc280fd19ba84003ecff85)
• OS X, 64-bit (Hash: d6c776878fd3d47f149fc9be4e76cf2d03d5a725)
• Linux, 64-bit (Hash: 4149de91c10b56ff091070acca80d233fbd5a797)