Block Bitcoin Engineering advisory on Coldcard RNG flaw. libngu incorrectly checks whether hardware-RNG macro is defined rather than enabled; falls through to MicroPython Yasmarang seeded from MCU UID and timer. Mk2/Mk3 v4: deterministic for known UID. Mk4/Q/Mk5: secure-element entropy hashed to 4 bytes; reseed replaces one 32-bit word → at most 2^32 streams. Active exploitation underway July 30. Block scope broader than Coinkite Mk3-focused warnings. Firmware update does not repair already-generated weak seeds.