In a nutshell: In recent years, we've seen more than a few CPU scams, with targets ranging from the Ryzen 7 1700 to the i9-9900K. In most cases, these chips are purchased by unscrupulous individuals and then replaced with doctored counterfeits, with the intent of a RMA scam. More often than not, the fake CPUs end up back in retail channels for unassuming customers to buy.
It seems there's an abundance of counterfeit Intel chips going around in China, as reported by HKEPC, a Chinese tech publication based in Hong Kong.
As the report notes, fake processors aren't altogether uncommon in Chinese markets (or others, for that matter). For instance, users on HKEPC's forums reported buying fake i7-8700K CPUs last year, and there was a Reddit user in the UK who also seemingly ended up with a fake i7-8700K around the same time.
In the case of the latter, what was supposed to be an i7-8700K turned out to be a Celeron D 336 -- a 90nm chip that debuted in 2004 and has long since been discontinued. Similarly, last year news broke of a user in Spain being scammed into buying a fraudulent i9-9900K, which apparently turned out to be a Core 2 Duo, another ancient chip. In both of these cases, orders were allegedly sold and fulfilled by Amazon, rather than a third party seller on Amazon.
Although, this wasn't the first time an old Celeron had been caught masquerading as a different chip. In 2017, reports of fake Ryzen 7 1700 CPUs on Amazon surfaced, where users were receiving old Celerons forged to look like Ryzen 7 chips.
Circling back to China, it seems there's a spike in CPU scams, with recent tactics involving altering the IHS of a Pentium Gold G5400 to resemble that of the more potent (and expensive) i7-7700K. Both of these chips are built on a 14nm process and use the same LGA packaging (FC-LGA14C) with the same dimensions and IHS. So, swapping the heat spreader through a delid would be feasible, and likely convincing assuming the quality of the relid. It's also possible that the IHS is being lapped and buffed, then re-etched.
HKEPC reports that these fraudulent chips are surfacing with retailers such as AliExpress and Amazon, and there's even reports of buyers receiving chips that have had the CPU die itself removed. Moreover, there have been attempts to RMA the affected chips through Intel. It isn't clear if merchants are trying to RMA the chips, or if resellers are maliciously trying to RMA them. Either way, Intel is unsurprisingly refusing to honor any RMA requests for chips that have been tampered with.
While there's nothing that suggests this scam has made its way west, it's always a good practice to remain vigilant. Avoid unknown third party sellers, and weigh second-hand hardware purchases carefully.