A software flaw in popular cryptocurrency storage devices allowed “numerous” hackers to steal more than $100 million in bitcoin, and more attacks targeting digital assets are ongoing, according to a crypto research firm.

A software flaw left cryptocurrency wallets vulnerable for thousands, a crypto research firm found.

Galaxy Research said Monday it identified 1,596 bitcoin, valued at about $102 million as of Tuesday, that had been stolen from more than 7,300 crypto wallets across three confirmed waves of theft and 14 smaller incidents.

A firmware flaw in Coldcard hardware wallets—a small, secure device that stores the secret recovery phrase used to secure bitcoin—left the wallet seeds weak enough for hackers to guess, Galaxy Research found, and Coldcard maker Coinkite confirmed last month a bug affected some firmware versions before releasing a fix.

Coinkite warned that updating the firmware would not repair compromised seeds, and that users should migrate their funds to a newly generated wallet.