Two major trading platforms — Binance and Polymarket — were investigating security incidents on Thursday, with the former facing potential losses in the billions. There’s no evidence the incidents were related.

Binance, the world’s largest cryptocurrency exchange by trading volume, said it was actively investigating reports of a “potential security issue.”

In an update late Thursday, Binance said that its initial investigation suggested that the incident may involve a compromised development operations engineer’s laptop. This allowed an attacker to access a service container and submit unauthorized withdrawal transactions.

“We have found no evidence of any wallet private key leak,” the company added.

Binance said the estimated total impact is about $6.3 billion, and it has worked with its blockchain partners to freeze around $3 billion in assets so far.

“Binance will cover all losses,” Binance said on X. “As a precaution, all deposits and withdrawals are temporarily suspended while our team conducts security checks, freezes funds, and works with law enforcement.”

The company did not respond to a request for comment.

Binance founder and former CEO, Changpeng Zhao, said on X a hack seemed likely.

“User funds are safe! It does look like a hack on Binance,” Zhao wrote in a post on X. “I don’t manage Binance anymore, but as a shareholder, I expect all user funds will be fully covered.”

Zhao expressed appreciation to Tether and Circle, issuers of cryptocurrencies traded on Binance, for quickly freezing funds.

Tether CEO Paolo Ardoino said on X the company froze more than $1.5 billion related to the potential Binance hack. Circle CEO Jeremy Allaire said the company froze over $800 million in connection with the incident and that it was coordinating with law enforcement.

Polymarket also reported a security incident

Also on Thursday, Polymarket, the world’s largest prediction market by trading volume, temporarily halted trading after users reported unauthorized withdrawals.

The company said in a statement on X that one of its third-party providers was compromised and that the incident had been referred to law enforcement. It also said trading had resumed by 3 p.m. Eastern time.

A Polymarket spokesperson told Business Insider that the malicious activity occurred in the UK and that the company will reimburse affected users. The company was unable to confirm the amount that may have been stolen.

Polymarket’s US exchange was not halted and did not appear to be affected.

A person familiar with the matter attributed the Polymarket hack to a compromised third-party provider called DebugBear, a web performance monitoring platform designed to help businesses optimize website speed. It’s unclear exactly how Polymarket uses the platform.

DebugBear did not respond to a request for comment. The company said in an X post on Thursday that it was aware of a security incident and was treating it as a “top priority.”