OneKey founder Yishi issued an urgent warning that older iPhones may be unsafe for storing cryptocurrency cold-wallet credentials, including seed phrases. The checkm8 vulnerability affects the BootROM of iPhone 4S through iPhone X, while usbliter8 affects the iPhone XS, XR, 11 series and second-generation SE. Because the flaws affect underlying boot code, iOS updates cannot remove them. An attacker with brief physical access can use a custom USB tool in DFU mode to execute code before iOS starts, potentially exposing stored seed phrases without leaving visible evidence. Airplane mode and factory resets do not prevent the attack. Yishi advised affected users to create an entirely new seed phrase on a secure device and migrate assets immediately, rather than restoring backups or generating new addresses under a compromised seed. He also recommended a long alphanumeric passcode, Lockdown Mode, personal chargers and current iOS software. Yishi had previously recommended using an iPhone as a cold wallet, but limited that advice to the iPhone 17 or newer.