Bitfinex

What happened

A security breach in Bitfinex's multi-signature wallet setup let attackers drain a large share of customer bitcoin in a single incident. The exchange spread the loss across all users' balances and later repaid affected customers over several years.

What to take from it

Even a widely used, multi-signature custody setup is only as strong as the systems and partners it depends on — 'multi-sig' alone isn't a safety guarantee.

Dates and figures are widely reported public estimates from coverage at the time, not KripZen's own audited data.