On January 15, Ethereum’s developers put out a security alert that they were postponing the scheduled Constantinople upgrade. Not everyone made the appropriate changes, however, and there is a currently a parallel universe of Ethereum mining. A “chain split” has occurred, and some miners are mining the unofficial Constantinople chain without consensus from the majority of the network.
The delay came after potential vulnerabilities were discovered in one of the new upgrades. As the statement delaying the fork says: We are investigating any potential vulnerabilities and will follow with updates in this blog post and across social media channels.
Out of an abundance of caution, key stakeholders around the Ethereum community have determined that the best course of action will be to delay the planned Constantinople fork that would have occurred at block 7,080,000 on January 16, 2019. People need to install a new version to avoid violating consensus.
It seems not all of the miners got the message. At least 10TH/s worth of mining power was still mining the unofficial chain at the time of writing, according to a fork monitor owned by Ethdevops.io