Parent was referencing trusted contexts: the default password printed on your wifi router, the bill a cashier just handed you for what you just bought, the legal papers you just signed, etc. The QR code just links the trusted document with trustworthy digital versions & extended content.

I'm not worried a spammer is going to get a bogus QR printed on the grocery store receipt I just received. I'm not going to scan QR codes printed & posted on subway walls for no apparent reason.

I was visiting a nature reserve where the trail opened to a resting area with some seats. A tree had a woodcut QR code on it, so I thought I'd scan it to find out more about the area.

Turns out, the QR code linked to some tracking site with a short URL. Even worse, the short URL had since been deleted, so I have no way to know the original URL it went to.

Nope. I go to the sender's URL manually and look for what it is they sent an email about.

Also, as to something like a javascript exploit in a URL itself, QRs can hold a surprising amount of data, enough to max out most URL browser limits around 2,048 bytes.

This is functionally the same as hovering over links in emails, which is the context in which I made my comment.

Users cannot check if a domain is "ok" by looking at it. You visit websites to discover what's there. A few years ago it was common knowledge that ".to" is shady and ".com" looks more legit. Now we have more TLDs than I can count. How is someone supposed to check that with visual inspection?

The way it should go: you scan a QR code. It gets interpreted into something useful that doesn't cause harm.

"Hey this QR would cause a 5€ transaction to Jon Doe. OK?" That's something the user can decide upon. payment://jon-doe:5€ doesn't help much.

(Edit: reading your post again, I realize it might be exactly what you have in mind)

Just compare with today's internet advertising. Legit websites are still full of somewhat malicious ads. And users click on it - of course, since that's what a website is for.

What I'm trying to make clear is that there is no such case where QR scanners, browsers or application may consider a safe context where the user implicitly consents with malicious actions by the QR/website/...

In a world where browsers are vulnerable to remote code execution, and a world where users do not run the latest version of a browser, and in a world where zero days exist in browers, it absolutely does matter.

Worked great for me on my last phone, and peace of mind knowing you aren’t being tracked.

Available to download on fdroid or the play store.

https://github.com/SecUSo

But QR code are not just for URL, they can contain up to 7k, which is a lot for text and numbers. And you can have several of them, use compression, etc.

Have you never come across phishing scams that looked eerily authentic only to be clued in by the fake url? I can read the URL before going to the website, and unless QR codes have a step where you have to manually confirm going to the url provided by the code (most don't) then that's a security risk

Not that it matters much for most users, as I said earlier, they blindly type url. They have no idea what it is.

You could put a warning saying "are you sure, this is going to kill your mother and steal all your money" and people would click on it if it's easy to do.

Nothing.

Nothing deterred the users. Warning dialogs were clicked past, obvious problems or mismatched information was ignored. The only way to stop users from giving their credentials to bad guys was what I call Brick Wall UX. The browser has to stubbornly refuse to let you do it. Unable to complete their task the user at last gives up.

This is a teachable moment. Your users are probably not going to be smarter, better informed or more cautious at least on average than in this test.

You must have some super-human ability to read a computer's mind if you can grok the kind of urls that usually come in emails like https://tinyurl.com/uvc58uq

Of course, if the email actually has a unique URL per recipient, then doing this gives away the fact that you interacted with the email.

The cost and risk of putting a sticker on a wall is much greater that that of sending a spam email. Legitimate advertisers already hire people for >$0 to do that. Illegitimate ones risk personal criminal prosecution because they have to be physically present.