Hackers gained access to Deribit’s hot wallet on Monday, promptly stealing $28 million worth of cryptocurrency.

On Wednesday, the industry’s largest crypto options exchange disclosed that its hot wallet had been compromised shortly before midnight UTC on Nov. 1. It assured users that all funds were safe and covered by company reserves. 

“It’s company procedure to keep 99% of our user funds in cold storage to limit the impact of these type of events. The hack is isolated & quarantined to our BTC, ETH and USDC hot wallets,” tweeted Deribit

The platform paused deposits and withdrawals immediately after the incident, later resuming the functions  after determining everything was safe.

Withdrawals were also briefly halted for third-party custodians including Copper Clearloop and Cobo, with the latter saying it received an unusual request for a fund transfer from Deribit at around 1 am UTC. 

“Cobo’s system automatically detected anomalies in the request and notified Deribit. The withdrawal is halted,” said Cobo in a statement.

Derebit will cover the loss of funds with its reserves – not from its $40 million insurance fund. The company said that it is still financially sound and will continue operating as normal. 

Wednesday’s hack follows weeks of consecutive exploits across the crypto space, with more than $718 million stolen in the last month alone, according to data from blockchain analysis firm Chainalysis. The analytics company described October as “the biggest month in the biggest year ever for hacking activity.”