Some days ago, a 51% attack on the Ethereum Classic network stole 1.1 million worth Ethereum Classic coins. Moments after the attack, coinbase posted a blog about it to raise awareness. The news than spread quickly to the wider crypto community. Here's the blog post by Coinbase on their official medium handle.
The reason for the attack is pretty easy to understand. Ethereum Classic's proof of work algorithm is very weak. Since it is a low market cap coin, there aren't much mining hash power going into mining it. It is also prone to being nicehashed.
"Nicehashable" means whether a crypto is vulnerable to 51% attacks by renting hash power on nice hash. And Ethereum Classic is unfortunately one of those cryptocurrencies that can be nice hased. Which obviously makes it an easy target.
Anyone with the proper programming knowledge and some money can attack Eth classic. Sometimes I wonder why this chain even exists. Its development is stalled, it is insecure but it still has some value. Speculation I assume.
Futher reading about the attack:
https://np.reddit.com/r/EthereumClassic/comments/adgg98/etc_under_51_attack/