No SSL validation? Prone to man-in-the-middle attacks?

Does the MQTT client do validation of SSL certificates on an ESP32 or a Raspberry Pi Pico? I see this note in the [MicroPython ssl documentation](https://docs.micropython.org/en/latest/library/ssl.html):

> Warning: Some implementations of ssl module do NOT validate server certificates, which makes an SSL connection established prone to man-in-the-middle attacks.

No files or tests are named. Start by locating the MQTT client's SSL setup for ESP32 and Raspberry Pi Pico and compare it with MicroPython's ssl certificate-validation behavior. Done means documenting whether server certificates are validated on each target and identifying the needed follow-up.

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