Cosmos Hub, the interchain proof-of-stake blockchain protocol, was down for around four hours on Wednesday after a bug was discovered during the deployment of a network upgrade.

“During the v17 upgrade, the Hub validators patched a security vulnerability in the Liquid Staking Module (LSM),” wrote the Cosmos Hub team on X.

If not patched, the security issue would have allowed users to evade slashing penalties by tokenizing shares in the process of redelegation. 

Cosmos developers identified and deployed a fix for the bug within the next two hours, but the chain did not resume producing blocks until the majority of validators had implemented the patch.

“The previous issue has been patched & the Cosmos Hub is producing blocks once more,” said the Cosmos Hub team in an X update at around 8:00 pm ET, noting that developers would be releasing a post-mortem on the issue shortly.

Cosmos Hub plays a central role in the Cosmos blockchain ecosystem, and is the main public blockchain of the network, which allows different networks to communicate with each other. It also serves as a decentralized exchange that allows users to transfer the network’s native token ATOM to US dollars.

The v17 upgrade would implement the features laid out in a “partial set security” proposal to the network, which would allow every consumer chain to be secured by a subset of the provider validator set. This would solve for a large number of validators being forced to validate chains they have no interest in securing, and bring down the cost for smaller validators to secure additional chains. 

A recent report from S16 Research Ventures found that Cosmos Hub was the second most frequently used chain in the ecosystem after the leading decentralized exchange Osmosis.

The price of ATOM was relatively stable during the chain outage, and was trading at $8.68 at the time of writing, up a little over 1.5% over the last 24 hours.