Greetings,
Since this is localized, it looks like either impact damage or some type of LCD failure. Maybe done by a fingernail, etc? Might just be a defect too.
It doesn't look like a ribbon or connection issue, or you would see some sort of unified lines or banding. You can also test by rotating and moving the LCD, but I suspect it will not change.
The camera will require inspection, a quote and service.
Canon Support | Service & Repair | Canon U.S.A., Inc.
~Rick
Bay Area - CA
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Danny
