Polygon network back up with a 'temporary fix' after eight-hour stoppage

Ethereum scaling project Polygon's blockchain network was down for roughly eight hours last night due to a technical upgrade that went wrong. 

The network has now been restored with a "temporary hotfix," according to a tweet from the company. 

Polygon co-founder Mihailo Bjelic told The Block that the project's proof-of-stake blockchain network has two layers: Heimdall (the consensus layer, based on Cosmos SDK/Tendermint) and Bor (the block production layer, based on Geth). A "small upgrade" on the Bor layer led the Heimdall layer to get stuck and the network stopped producing blocks, said Bjelic.

The upgrade was not supposed to impact the consensus layer "in any way," according to Bjelic. But since it did, the network stopped working from 5:50 PM UTC Thursday to around 1:50 AM UTC Friday.

Bjelic did not detail the temporary fix but said it was introduced "as soon as possible" to get the blockchain up and running again. "No user funds were at risk at any moment," he said. A permanent fix, which requires wider action from validators and is basically a network upgrade, is expected today or tomorrow.

Polygon is one of the biggest blockchain ecosystems, with over 7,000 decentralized applications built or building on the network. The outage comes a few months after Polygon was at risk of losing nearly all of its MATIC tokens, worth $24 billion, in December.

At the time, Polygon's proof-of-stake genesis contract contained a critical bug that could have allowed attackers to arbitrarily mint all of Polygon's more than 9.2 billion MATIC tokens from its MRC20 contract. The project undertook a hard fork to fix the bug at the time, but before it deployed the fix, a malicious actor stole 801,601 MATIC tokens, worth over $2 million at the time. 

Bjelic at the time said Polygon is "investing much more in security," but issues keep cropping up for the network.