Coinbase User? Your Contact Details May Have Leaked Through a Vendor

Coinbase said a breach at analytics provider Amplitude exposed contact information for some customers. The exchange said its own systems saw no unauthorized access and customer funds remain safe.

The disclosure lands a day before Coinbase reports third-quarter earnings. Meanwhile, South Korean exchange Bithumb confirmed a breach of an internal system used by its staff.

Coinbase Names a “Small Subset” but No Number

Coinbase gave its account of the incident in a short post from its support account on X.

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Coinbase has not had a data breach. Amplitude, an analytics vendor, experienced a security incident which impacted a small subset of Coinbase customer contact data, among other Amplitude customers. We’ve found no evidence of unauthorized access to Coinbase systems, and…

— Coinbase Support (@CoinbaseSupport) October 28, 2026

The post did not name the exposed contact fields. An anonymous X account claimed attackers obtained details for more than 70,000 users. 23pds, chief information security officer at security firm SlowMist, reshared the claim. 

Coinbase has not confirmed any figure yet. BeInCrypto has reached out to Coinbase for comment.

Coinbase has faced attempts to turn customer data against its users before. In May 2025, the exchange said criminals bribed overseas support contractors to gather customer records for impersonation scams.

The latest disclosure comes just before Coinbase’s next financial update. The exchange reports third-quarter results after the market closes on Thursday. Analysts expect revenue near $1.2 billion.

The incident came after the quarter closed on September 30, so any cost would more likely appear in fourth-quarter results. Still, a cost estimate in Thursday’s update would show whether the incident reaches Coinbase’s books.

Bithumb Says the Breach Stopped at Its Staff System

Coinbase is not the only exchange handling a leak this week. In South Korea, Bithumb said an unauthorized outside party accessed its mobile groupware system employees use internally.

The exchange reported it to the Korea Internet & Security Agency (KISA).

“So far it appears to be focused on internal employee information, but we are analyzing the details while leaving open the possibility that member information was included,” a Bithumb official said.

Bithumb added that the work system sits apart from its trading system. It said customer crypto assets therefore cannot be reached through this breach.

Its history shows how leaked contact details can turn into losses. In 2017, a database stolen from an employee’s computer exposed phone numbers and emails for about 3% of customers. Bithumb later tied wallet thefts to phishing.

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