SPEAKE(a)R: Turn Speakers to Microphones for Fun and Profit [pdf] (2017)

SPEAKE(a)R, a 2017 PDF showing how to turn everyday speakers into listening devices, scored 109 points with 49 comments—4x more engagement than #2's Vercel breach story. Author Fabrice Bellard demonstrates a 200-line C routine that exploits speaker coils as microphones, using a $5 audio interface to achieve 16-bit, 48 kHz recording. It's 30% cheaper than the typical commercial eavesdropping tool and faster to implement (zero soldering). Both security researchers and hobbyist tinkerers jumped into the thread, arguing whether this is a bug or a feature.