An employee demonstrates the waterproof feature on the Samsung Electronics Co. Galaxy S7 smartphone during a media event in Seoul, South Korea.

Samsung's Galaxy S7 smartphones contain a microchip security flaw, uncovered earlier this year, that put tens of millions of devices at risk to hackers looking to spy on their users, researchers told Reuters.

The Galaxy 7 and other smartphones made by Samsung Electronics were previously thought to be immune to a security vulnerability known as Meltdown, which researchers said affected most of the world's PCs, smartphones and other computing devices.

Researchers from Austria's Graz Technical University told Reuters they have figured out a way to exploit the Meltdown vulnerability to attack Galaxy S7 handsets.

The team plans to release their findings on Wednesday at the Black Hat security conference in Las Vegas. They are looking into Meltdown's impact on other makes and models of smartphones and expect to uncover more vulnerable devices in the near future, researcher Michael Schwarz told Reuters.

"There are potentially even more phones affected that we don't know about yet," he said. "There are potentially hundreds of million of phones out there that are affected by Meltdown and may not be patched because the vendors themselves do not know."

Samsung said it rolled out patches in January and July to protect Galaxy S7 handsets against Meltdown.

"Samsung takes security very seriously and our products and services are designed with security as a priority," the company said in a statement.

A Samsung spokeswoman did not comment on how many Galaxy S7 smartphones had been sold.

She said there were no reported cases where Meltdown had been exploited to attack an S7 handset and that no other Samsung phones were known to be vulnerable.

Meltdown, and a second vulnerability known as Spectre, can be exploited to reveal the contents of a computer device's central processing unit - designed to be a secure inner sanctum. Hackers can exploit those vulnerabilities by either bypassing hardware barriers or tricking applications into giving up secret information such as passwords or banking details.

There are no known cases of hackers exploiting either vulnerability in a real-world attack, but disclosure of the widespread hardware flaws has rocked the computer industry, forcing chipmakers and device manufacturers to scramble to contain the fallout.

The Galaxy S7 is currently used by some 30 million people, according to research firm Strategy Analytics. Samsung has released two new versions of its flagship Galaxy line of smartphones since the S7 debuted in 2016.