Vadim Makarov writes "Physics World reports on researchers demonstrating a full eavesdropper on a quantum key distribution link. Unlike conventional exploits for security vulnerabilities that are often just a piece of software, spying on quantum cryptography required a box full of optics and mixed-signal electronics. Details are published in Nature Communications, and as a free preprint. The vulnerability was known before, but this is the first actual working exploit with secret-key recording confirmed. Patching this loophole is in progress. Disclosure: I am one of the researchers who worked on this."