This happened to me exactly the same 1 minute ago.
I got the notification that it was added immediately after I opened Creative Cloud. Is that the reason?
I will disable it until we know.
Open can be used to launch apps in hidden mode, as explained here https://forums.macrumors.com/threads/login-items-hide.2366349/post-31680952
Check ~/Library/LaunchAgents/
Check /Library/LaunchAgents, /Library/LaunchDaemons and /Library/PrivilegedHelperToolsThank you. I'm afraid nothing was in ~/Library/LaunchAgents
com.adobe.AdobeCreativeCloud.plist
com.adobe.ARMDC...43c37a23d420d.plist
com.adobe.ccxprocess.plist
com.fujitsu.pfu.ScanSnap.AOUMonitor.plist
com.fujitsu.pfu.SshRegister.plist
com.fujitsu.pfu.SshResident.plist
com.fujitsu.pfu.SshSCloudWatch.plist
com.google.keystone.agent.plist
com.google.keystone.xpcservice.plist
com.microsoft.update.agent.plist
com.adobe.acc.installer.v2.plist
com.adobe.ARMDC.Communicator.plist
com.adobe.ARMDC....JobBlessHelper.plist
com.google.keystone.daemon.plist
com.microsoft.autoupdate.helper.plist
us.zoom.ZoomDaemon.plist
com.adobe.acc.installer.v2
com.adobe.ARMDC.Communicator
com.adobe.ARMDC.SMJobBlessHelper
com.microsoft.autoupdate.helper
us.zoom.ZoomDaemon
It might be one of the Adobe ones, as you have 5 listed in settings and 6 in total in /Library/LaunchAgents & /Library/LaunchDaemonsCreative Cloud