If it only started after the update, it could be a Windows bug rather than malware. You should try restarting your PC first, then check if there are any newer Windows or Defender updates available. You could also restart Windows Explorer from Task Manager to see if that clears it up. If it keeps happening, it would help to know if it's opening the same windows every time or only after startup.
Multiple windows keep opening after windows update on Tuesday
Crawford, Leslie
0
Reputation points
After installation of MS Update, Installation Successful: Windows successfully installed the following update: Security Intelligence Update for Microsoft Defender Antivirus - KB2267602 (Version 1.455.439.0) - Current Channel (Broad)
Multiple windows open starting with START > Notifications > Desktops. I believe this was a security udpdate and it is behaving like malware. I have verified no malware installed.