The newest version of the Login One! Standard (freeware) plug-in for J3 has been released today. It resolves the issue mentioned by poster. Please update by clicking the "Is this the latest version" link in the current install of the authentication plug-in (Joomla! back-end authentication plugin manager) and follow the instructions on your screen.

Thank you for your post. You are completely right. A corrected version (v1.3.7) of the plug-in will be released very soon. Please install the new version on top of the existing one. Your settings will be kept. We appologise for the hassle.

The helpers folder is missing from the plugin plg_loginone_user_J30_1362.zip causing an error message when logging out of the administrator backend.