During installation, the router sent several data packets to an Amazon server in the US. These packets contained the configured SSID name and password in clear text, as well as some identification tokens for this network within a broader database and an access token for a user session that could potentially enable a MITM attack.
Linksys has refused to acknowledge/respond to the issue.
This is what I’m thinking too. The only likely scenario under which the plaintext and MITM words make sense together is HTTP. I wouldn’t put it past Linksys to have used an HTTP API endpoint but these days a lot of things scream if you use HTTP. Thanks for the work!