[rickdeckard]

Usually the advertised price must be honored, because it may have brought the customer to your store.

For prices displayed on the shelf-label inside the store the law is usually not that strict (YMMV), as a shop-owner can refuse sale on check-out (otherwise I could put a pricetag on e.g. a shopping-basket and the shop-owner would be legally required to sell me the basket...).

Besides, most shops I've seen (in Europe) already moved from Infrared communication to RF (NFC or proprietary), for centralized shelf-label management without handheld devices. So all this study (and the underlying reverse engineering of the IR-protocol) might do is probably accelerate the transition from IR to RF-based ESL...

[rimunroe]

> Usually the advertised price must be honored, because it may have brought the customer to your store.

This is not the case for groceries in Massachusetts at least. If there’s a discrepancy between the tag’s price and the scanned price the store must charge the customer the lowest of the two: https://www.mass.gov/price-accuracy-information

[devilbunny]

I suspect this law does not apply in cases of fraud. If not, simple tag-switching would be rampant.

[otterley]

There is, as you suspect, a carveout:

https://malegislature.gov/Laws/GeneralLaws/PartI/TitleXV/Cha...

(i) ...if there is a discrepancy between the advertised price, the sticker price, the scanner price or the display price and the checkout price on any grocery item, a food store or a food department shall charge a consumer the lowest price. If the checkout price or scanner price is not the lowest price or does not reflect any qualifying discount, the seller: (i) shall not charge the consumer for 1 unit of the grocery item, if the lowest price is $10 or less; (ii) shall charge the consumer the lowest price less $10 for 1 unit of the grocery item, if the lowest price is more than $10; and (iii) shall charge the consumer the lowest price for any additional units of the grocery item. For the purposes of this subsection and unless the deputy director determines otherwise, individual items that differ only by color, flavor or scent shall be counted as the same item if they are identical in all other aspects, including price, brand, and may only vary in random weight. This subsection shall not apply if: (1) there is evidence of willful tampering; or (2) the discrepancy is a gross error, in that the lowest price is less than half of the checkout price and the seller, in the previous 30 days, did not intend to sell the grocery item at the lowest price.

[bee_rider]

I dunno, having worked in retail I think it is just not that hard to steal in general (I wasn’t going to get killed over some bananas). Most people are honest most of the time.

The law probably doesn’t apply to fraud, but then the cashier only notices the really obvious cases.

[drdec]

They are talking about the price on the shelf vs the price at the register. The price tag on the shelf has information identifying the product. The price at the register is obviously associated to the bar code on the product. So there's no way for a consumer to swap price tags from one product to another.

Source - worked at a grocery store in Massachusetts as a teen

[devilbunny]

I was being colloquial by referencing the pre-scanner way of doing it, but since this article is all about changing the shelf tag, it seemed relevant.

[MetaWhirledPeas]

But in the moment how do you know it's fraud and not an employee mistake? Especially if the price is not egregiously low.

[rimunroe]

The thing I was responding to was about pricing policy in general, but I would assume so

[stevekemp]

I recently learned that in some cases fines of mispriced goods were very low, leading to companies repeatedly failing tests - and over/undercharging their customers.

https://www.theguardian.com/us-news/2025/dec/03/customers-pa...

That seems shocking to me, but I guess I live in a country where the prices on the shelves are "final" (with no need to add taxes) and I think it would be immediately obvious if I'd been charged the wrong price for goods.

[teeray]

It definitely varies by jurisdiction, but the register price always loses to any printed price in the US states I’ve lived in. This is a protection since retailers have used pricing mistakes to unfairly profit. Watch your receipt like a hawk at the dollar store[0]

[0] https://www.theguardian.com/us-news/2025/dec/03/customers-pa...

[master-lincoln]

How is the transport medium changing anything?

To me this is about having protocols that are suitable so not anybody can write to these labels without knowing a store secret or using replay attacks.

[mschuster91]

> How is the transport medium changing anything?

it's mostly about efficiency. IR based, an employee needs to physically walk around. RF based, place a transmitter or two in the building and the system now works fully automated.

[master-lincoln]

Sorry about not being explicit. I meant how it changes anything security-wise.

With the same vulnerable protocol the RF system is as easy to attack with bigger consequences then it seems....

[rickdeckard]

The RF system doesn't use the same protocol, it's a new protocol (to potentially hack and reverse-engineer).

The early shelf-label systems were IR-based, sold in bulk and were programmed manually using handheld devices held against them.

Most shelf-label solutions of today are part of a service-model, where gateways are mounted in the store to wirelessly update any label on price-change, often orchestrated remotely so store-chains can update all shops simultaneously.

[ornornor]

Very much depends where. In QC, if it rings higher than tagged in the store you get the first one for free and the next ones at the lower price. They take it VERY seriously as a result and will take the tag down while they make a new one to ensure nobody else gets a freebie.

Stores hate giving the product away and pricing errors are much lower in my experience.