Many WiFi access points have Bluetooth built into them now, and Bluetooth chips typically have firmware of their own.
In this case, a software stack called “BLE-STACK” that runs on a Cortex-M3 MCU.
So far, it seems to impact various Cisco, Meraki and Aruba access points.
Why are there Bluetooth chips in enterprise/commercial grade wifi APs? From Ars:
The BLE chips offer a variety of enhancements to traditional Wi-Fi APs. Retailers, for instance, can use them to monitor customer movements inside stores by monitoring the Bluetooth beacons sent by the customers’ phones. Hospitals can use BLE to keep track of Bluetooth-enabled medical equipment.