Microsoft Edge Canary build users were facing a serious inconvenience over the weekend. After the Edge was started, the browser started opening windows, seemingly at random. After 5 minutes or so, users will have 6-7 new Edge windows apart from the one they opened intentionally. Today, Microsoft released a new Edge Canary build to fix the issue.
You can update to Edge version 1008 to fix this random window issue.
Source: Microsoft