Registration form issue

Hello there.

Initially I wanted to send a e-mail, not post here, but here is the issue. One of my clients has ultimate member installed. She never had any issue with it until a couple of weeks ago when she forwarded me a e-mail(the ultimate member mail template) that a new user was registered with the administrator role. My hunch was that it was the ultimate member registration form, but I was not sure since I haven’t seen any updates or reports regarding any security issues. I installed activity log so I can track what’s happening on her website and today it happened again, and this is what Activity log registered: https://prnt.sc/ddIExd2Syn3G . Do you know if any of your clients has the similar issue? Besides WooCommerce and Ultimate member there is no other plugin that would trigger any username creation. Note that I also tried to create usernames myself via ultimate member registration form and the log in the activity log looks the same as the screenshot. Usernames created by executing wp_insert_user for example directly from functions.php or any other location are not logged in the activity log file so a hacking via file editing is excluded.