Coinbase Support stated on Oct 28 that Coinbase itself "has not had a data breach." Per that statement: analytics vendor Amplitude had a security incident that "impacted a small subset of Coinbase customer contact data, among other Amplitude customers"; Coinbase found "no evidence of unauthorized access to Coinbase systems"; "customer funds were not impacted"; and Coinbase is "notifying impacted customers and regulatory agencies in accordance with our legal obligations."

Separate social posts claimed ~70,000 users or a Coinbase systems breach; those figures are not in Coinbase's statement and are unverified here. If you are a Coinbase customer: watch for Coinbase's own notification, treat unexpected "verify your account" mail/SMS as phishing, keep phishing-resistant MFA on, and do not move funds because of rumor posts. Other Amplitude customers should ask Amplitude whether their tenants were in scope.