Apple handsets have been damaged as fans have fallen for a viral advert claiming that the software update made the iPhones waterproof.
The "advert" circulating on social media sites claims that updating devices with the operating system installs a "smart switch" that cuts off the phone's power supply when water is detected.
This, it claims, "prevents any damage to your iPhone's delicate circuitry".
The advert looks very similar to an authentic Apple advertisement, with the same plain white background and minimalist style.
Users have dunked theur gadgets into water to test out the new feature, only to find their devices rendered completely useless.
One user wrote on Twitter: "Whoever said iOS 7 was waterproof **** you."
Another wrote: "OK whoever said iOS 7 is waterproof GO **** YOURSELF."
The prank idea is believed to have originally started on the controversial forum 4Chan.
The iOS 7 software was released last week, and is available as a free upgrade for newer models of the iPhone and iPad.
It was released shortly before the new iPhone 5S and 5C models went on sale.
The 5S features a fingerprint unlocking device for extra security. However, a group of German hackers has found a way to bypass the measure.
The Chaos Computer Club uploaded a video of them managing to fake a fingerprint and unlock the device.