The camera of the desktop computer suddenly flashed. What happened?

Check whether there is poor contact first. Plug in the USB port of the camera and see if there is a flash.

Step two, check the software on your computer and see if there is any software to take pictures regularly.

Step 3: Have you installed the online chat software?

If all are excluded, check whether there are abnormal processes in the memory. Maybe it was attacked by a Trojan horse. And it's a malicious Trojan horse.