Are you sure you’ve NEVER shared the qr code with anyone? If so, what is it actually for? Because a qr code’s purpose is to be shared. If you’ve ever shared it before, people can have copies of it. I myself take a picture of a qr code and load it from my camera roll instead of directly opening the link from my camera, because I want to keep a copy of it.

Now if you truly haven’t shared it to anyone, then it is either a bug with whatever app, website, or mechanism you generated the qr code from and it’s alerting you; or it’s an IOS bug; with the former the more likely. Like others have said, this is absolutely not normal behavior on a non-jailbroken iphone. And to Apple’s credit, the iphone is pretty secure. This should be the order of steps before going nuclear:

• Find out if the source of the issue is the app or mechanism the QR code is using to alert you. Check if it’s a bug or it’s actually a malicious/rogue app.

• If that’s all good, clean up your phone. Check which apps have access to your camera and microphone, and disable anything you don’t need or trust. Delete apps if necessary.

• If that still doesn’t stop it, hard reset your phone.