That's what Safari autofills in some login forms on different websites:
It looks like a password of kind "Internet password" in Keychain. Safari autofills this information even tho there's a proper "Web form password" saved in my Keychain for each of those websites.
Isn't Safari supposed to only autofill "Web form password" passwords?
It' an old bug. Update safari to last version. Apple has released three updated versions of its Safari Web browser, which commonly address an issue where saved passwords would not be automatically into relevant password fields as expected. In addition to fixing how passwords are managed Apple issues fix for password autofill bug in Safari | MacIssues
Have you tried searching for the String/Username "MDoEEPg..." in your Keychain and deleted it?
I have also had this problem, and believe it originates from using Norton Identity Safe across Chrome & Safari.
I'm speculating here, but in my case the set-up was that Norton Identity Safe apparently used my login keychain for storing UUIDs, which (again, speculation) the NIS software would then look up in its encrypted online database and retrieve the valid website username & password.
Since setting up an iCloud account, I notice that new usernames and passwords get saved in my iCloud keychain instead.
As I was confident that all the user and password credentials I need are now in my iCloud keychain, the solution for me was to open Keychain Access and select login keychain at the top left, then filter the list and delete out the offending entries. These would be the ones marked as Kind 'Internet Password'; the corresponding credentials in iCloud keychain would be of the Kind 'Web form password'.
Hope this helps!
I don't know how to fix this problem on an existing system, but I bought a new Mac and started from scratch instead of migrating the system from the old Mac to the new Mac. I haven't had this problem ever since.
