MediaMarktSaturn, the German retail group behind the roughly 1,070 MediaMarkt and Saturn electronics stores across Europe, has pulled Ledger’s crypto hardware wallets from its shelves and websites as concerns grow about a supply chain attack on the French wallet maker. At the same time, Mark Karpelès, the former CEO of the infamous and collapsed Mt. Gox bitcoin exchange, says he has now examined a Ledger with an implant that was bought at Singapore’s airport.

Karpelès had been posting about Ledger devices fitted with “spy implants” as far back as last month, weeks before Ledger users’ wallets started getting drained on Friday, and his involvement in the uncovering of the supply chain attack on Ledger has…