An Unverified Password Change vulnerability exists in the embedded web servers in all Modicon M340, Premium, Quantum PLCs and BMXNOR0200 which could allow an unauthenticated remote user to access the password delete function of the web server.
https://www.tenable.com/security/research/tra-2018-38
https://www.schneider-electric.com/en/download/document/SEVD-2018-327-01/