https://motherboard.vice.com/en_us/article/ywkw9j/etherscan-l337-hack

An online panic ensued Monday morning when visitors to a popular blockchain explorer site for Ethereum were confronted with the cryptic pop-up displaying “l337,” or “elite” in old-school hacker speak, indicating that the site was compromised.

Blockchain explorers are web portals that anyone can use to view public cryptocurrency transactions—essentially, financial reporting sites for cryptocurrencies. Etherscan.io is an extremely popular explorer for Ethereum’s blockchain (ranked the 1,379th most popular site in the world according to Alexa), and when the message—basically international code for “you’ve been hacked”—popped up on the site, worried users took to Twitter warning others to stay away from the site.