An issue was discovered on Enphase Envoy R3.x and D4.x devices. There are hardcoded web-panel login passwords for the installer and Enphase accounts. The passwords for these accounts are hardcoded values derived from the MD5 hash of the username and serial number mixed with some static strings. The serial number can be retrieved by an unauthenticated user at /info.xml. These passwords can be easily calculated by an attacker; users are unable to change these passwords.