

Hundreds of millions. They’re used in an almost uncountable number of IoT devices.
It’s only this specific chip that is affected. It’s not all bluetooth chips. The article doesn’t even specify which of their tens of chips is affected; ESP32-D0WD-V3, ESP32-D0WDR2-V3, ESP32-U4WDH, ESP32-PICO-V3, ESP32-PICO-V3-02, or the ESP32-PICO-D4.
Even if it were all of them, and even if it were hundreds of millions of devices it would still pale in comparison to HeartBleed in all aspects. It’s an interesting but sophisticated attack vector which severely limits its usage. But lets say you execute a MITM attack from one of these ESP32 chips. What are you feasibly able to do? A MITM attack? Considering these are all low power devices its extremely unlikely that they would be able to output enough power to overtake your home AP. Without doing more research on it, the actual attack surface is opaque. I mean, I guess a guy in China can remotely turn on your sprinklers or get your WiFi password… Lot of good that’s gonna do him from China.
IMO this is a right of passage. Sure, windows babies you to the point where you can’t really mess much up, but that doesn’t mean its impossible to mess up. I’ve also borked Windows installs just by using them over long periods of time. You bork linux a few times and learn what not to do.