Relevance to DeepScreen settings; maybe that was what triggered it?
(Off Topic:) Use Alt+PrintScrn to capture only the avast window or any other window in the future. Highlight the window with your mouse by clicking it, and then use Alt+PrintScrn to copy the image. Paste image in Paint and save to desktop. You can either delete it or save to Pictures later after attaching it to your new post.
Ctrl+PrintScrn always captures the entire desktop.