🚨[Updated] Ethereum Classic has experienced “multiple 100+” reorg attack - Ethereum Classic claims not an attack, new miners being tested - Coinbase rebuts

According to block explorer and mining pool Etherchain, the Ethereum Classic ($ETC) blockchain appears to be experiencing a block reorganization attack. A tweet from the firm claimed "a successful 51% attack on the Ethereum Classic network with multiple 100+ block reorganization." A reorganization attack could potentially delay or reverse transactions on a blockchain. Around the same time, the official Ethereum Classic twitter account issued a bulletin to all exchanges and mining pools recommending that they increase confirmation times to over 400 blocks for withdrawals and deposits.

Update one: A tweet from Ethereum Classic now claims that believe the anomaly was related to a new ASIC miner being tested. The hashrate was likely selfish mining and no double spends have been detected according to the message.

Update two: Coinbase has released a blog post stating that there had in fact been a double spend equal to 88,500 ETC, and that a reorganization attack was ongoing.