A group of cybercriminals is demanding a $21 million ransom from a New York-based law firm representing megastars like Lady Gaga, Madonna and Elton John, according to The New York Post. The infiltrators, which are believed to be part of a group called REvil or Sodinokibi, claim to have stolen 756 gigabytes of data from Grubman Shire Meiselas & Sacks’ computers. They also claim that the data cache includes contracts, personal correspondence, phone numbers and email addresses.

Variety says the group already attempted to share a one-gigabyte collection of documents on Mega, but the file—sharing service took down the account. They also apparently released a screenshot of Madonna’s contract. A source told the Post that the hackers got in “while everyone was focused on the coronavirus.” The firm, which is reportedly not negotiating with the group, said in a statement:

“We can confirm that we’ve been victimized by a cyberattack. We have notified our clients and our staff. We have hired the world’s experts who specialize in this area, and we are working around the clock to address these matters.”

If REvil truly is behind the attack, then the law firm fell victim to the same group that targeted foreign exchange company Travelex earlier this year. The group claimed to have stolen 5GB of sensitive customer data from Travelex back then and demanded a $6 million ransom in exchange for not publishing it online.