Espressif have not released the sources of the WiFi implementation, just binaries. I would define that as "security through obscurity".
This is not to say that Espressif is the bee's knees. I personally wouldn't use their hardware in production. But by making their product easily accessible, and much of the source code open, they have made it easier for white hats to raise security issues.
[1] https://www.brothers-brick.com/2018/11/05/lepin-ordered-to-s...
[2] https://www.brothers-brick.com/2019/04/28/arrests-made-in-le...
https://github.com/espressif/esp32-wifi-lib/issues/2 https://github.com/espressif/esp-idf/commit/c1396830243b4c8f...