Use a better QR scanner app. I use Privacy Friendly Apps' "Privacy Friendly QR Scanner", which always presents you with the scanned URL or text in the app before doing anything, and asks you to verify that you want to visit the site. It also includes the ability to generate your own QR codes.
It's not very good, I just tried it on an image and it didn't work. The built-in iPhone QR code reader inside the camera app could pick it up without any issues.
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Use a better QR scanner app. I use Privacy Friendly Apps' "Privacy Friendly QR Scanner", which always presents you with the scanned URL or text in the app before doing anything, and asks you to verify that you want to visit the site. It also includes the ability to generate your own QR codes.
See https://secuso.aifb.kit.edu/english/105.php for that and other apps developed by that research group.
It's not very good, I just tried it on an image and it didn't work. The built-in iPhone QR code reader inside the camera app could pick it up without any issues.