Russian hackers are exploiting Signal Messenger’s “linked devices” feature to spy on encrypted conversations. By tricking users into scanning malicious QR codes, attackers can add their devices to victims’ accounts, enabling real-time message duplication and bypassing end-to-end encryption. Mandiant warns that this threat extends to other messaging apps like WhatsApp and Telegram, emphasizing the need for users to enable screen locks, update software, and regularly audit linked devices.