1Password explained its decision to nix the autosubmit function, citing user experience and safety reasons, such as malicious websites attempting capture your critical information in a false password field.
Mojave's functionality also came into play in the decision. Apple team lead Michael Fey wrote on the 1Password blog, "The mechanism by which 1Password was performing autosubmit is no longer supported in macOS Mojave. As yet another step towards a more secure environment, apps that can virtually type the 'Return' key on the keyboard have been significantly restricted."
In addition to the changes in user experience, 1Password announced that it is now notarized by Apple, meaning that Apple has endorsed 1Password as free of any malware.
Users who have purchased 1Password 7 or who are subscribers can update to 1Password 7.2 for free.