The urgent fix Apple released to address the root account vulnerability in macOS broke file sharing for users.
Mac owners reported that after applying Apple's security update yesterday, file sharing over the legacy Apple filing protocol (AFP) stopped working.
Connection attempts to file servers and networked computers using AFP would fail, even when the correct user credentials were applied.
File sharing using the server message block (SMB) protocol on macOS is not affected by the bug.
To fix the broken AFP file sharing, Apple advised users to open the terminal app and enter the command "sudo /usr/libexec/configureLocalKDC" and press return.
When prompted, providing the administrator password, pressing return, and quitting the terminal app will fix the problem.
Apple has similarly updated the security fix for the root vulnerability to address the file sharing issue.
Earlier this week, macOS users discovered the disabled root superuser account that gives full access to their computers could be enabled by simply trying to log on with the "root" user name.
The bug meant the root account was enabled with no password during local and remote logins. Alternatively, an attacker could set any password they wanted for root when the account was enabled.