why is there a rectangle box with red lines etched on my macbook screen

"Etched" implies an abrasive procedure applied to the display glass, permanently altering it. It would not normally be red though. If what you are seeing is an image on your screen, does it appear in a screenshot? If it does please post the screenshot here. Please don't post any information you might consider personal.

To learn how to capture, edit (if necessary) and post a screenshot to this site, please read the Appendix in Writing an effective Apple Support Communities Question - Apple Community. Refer to Screenshots (Mac).

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