I've got such problem.
I was signing into my account at one site, for example ***.mail.com (it has some subdomain). So i entered my login (as a login i had some email address at mail.com), password, clicked the entering button and Opera suggested me to update (not to save) my password. I clicked this suggestion, and Opera has updated my password with appropriate account name (my real email account on mail.com) on the second-level domain mail.com! And now i can't no longer login into it, because previous password has been replaced by the new one, i had entered at ***.mail.com. So is there any possibility to roll back this password update?
OS: Windows 8.1
Opera: it was some version of Opera 63