Bithumb, the second-largest cryptocurrency exchange in South Korea, disclosed on October 28 that an unauthorized external actor accessed its internal mobile groupware system, resulting in the exposure of personal data. The exchange stated that it is currently investigating the full scope of the compromise to determine if customer-specific information was included in the leak. This development follows a broader wave of security incidents affecting multiple financial institutions in the region, drawing immediate attention from regulators and industry leaders.

According to Yonhap News Agency, the breach was detected on October 27 when abnormal access patterns were identified within the company's in-house communication tools. While Bithumb has not yet specified how the system was breached or the exact volume of data exposed, an industry source told Yonhap that some customer personal information had indeed been leaked. The incident adds to a series of recent setbacks for the exchange, which has faced regulatory fines and operational errors earlier in 2026.

Regulators Inspect Multiple Breaches

The Bithumb incident is not isolated; it occurred on the same day that two other major South Korean financial firms reported similar data compromises. Daishin Securities announced that the personal information of 38,490 customers, including names, email addresses, and mobile phone numbers, was leaked after unauthorized access was detected. The brokerage stated it would compensate affected customers for any resulting damages in accordance with local laws.

Asset manager Mirae Asset Global Investments also confirmed a hacking incident, though specific details regarding the data involved were not immediately detailed. In response to these concurrent breaches, South Korea's Financial Supervisory Service (FSS) has begun on-site inspections. FSS Director Lee Chan-jin emphasized the need for stronger IT security, noting that the integration of artificial intelligence into hacking methods makes vulnerabilities easier to detect and simultaneous attacks more common. He urged corporate boards to take a leading role in enhancing their security capabilities.

Industry Warnings on Phishing Risks

Binance founder Changpeng Zhao highlighted the interconnected nature of these incidents in a post on X, listing the Bithumb breach alongside the Daishin and Mirae Asset incidents and a separate issue involving Coinbase vendor Amplitude. Zhao warned that leaked exchange data is predominantly used for phishing, SIM swapping, and social engineering attacks. He advised users to assume that any contact regarding account security or refunds is a scam, even if the caller knows personal details or recent transactions.

To mitigate these risks, Zhao recommended using unique email aliases for each exchange and avoiding text-message-based two-factor authentication. Instead, he suggested employing hardware keys or passkeys and requesting number locks from phone carriers. These recommendations align with broader industry advice following recent breaches at other crypto-related firms, including hardware wallet providers Foundation and Trezor, which reported phishing campaigns and data leaks in the past few months.