Multiple windows keep opening after windows update on Tuesday

Same problem. Windows 11 (Insider) installed an update yesterday. Suddenly have several problems that do indeed behave as malware. Started last night during a game. Several times opening a menu in the game would weirdly make the menu smaller, then refuse to exit. The game still runs, I can move around, just will not exit the menu. Figured I played too long...(;)) Switched off. Switched on today. On line teaching a class in tencent meeting. Opening files and photos at the same time. Had about 3 folders and 2 photos open. Out of no where photos.exe starts opening several new instances (I was just switching between folder and photos at the time. Not opening anything). It opened 300 new instances. Locked down my pc for about 20 seconds. Refused to open the quickbar. Extremely slow to open Task manager. Finally stopped, and I was able to kill the app from task master. Resolved the issue. For now. But for those 20 seconds....my heart was in my mouth. Really thought I had been hacked! Scanned with Avast. All clear. No other issues so far. But it is certainly annoying. As part of insder program I will keep using it and report any other issues. But my advice would be to roll back to before the update.

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.