Per this question in 2012, (Security risks of scanning an unknown QR code) there are a few big risks to scanning a QR code:
- Scanning a URL that links you to a malicious website
- Scanning a QR code that performs some automatic configuration (e.g. connecting to wifi, etc.)
- Scanning a maliciously-formatted code that can exploit the scanner app.
I didn't think items 1 or 2 were big issues, but I was surprised to learn that (as of this writing), the iPhone camera app does not allow users to inspect a URL from a QR code without opening it.
The only instance I know of for item 3 was the 2014 Nintendo 3DS game, Cubic Ninja. A 3DS could be "jailbroken" due to an exploit in the QR code scanner there.
I use a QR code scanner that returns the raw contents without any pre-loading of URLs or anything. So I feel relatively safe scanning QR codes.
With all this said, this is my question: Besides these three concerns, are there any other known risks to scanning an arbitrary QR code?