Tens of millions of Samsung Galaxy S7 phones are vulnerable to hackers who want to spy on users, according to new research. A microchip security flaw opens the phones up to a security vulnerability known as Meltdown, say researchers from Austria’s Graz Technical University. Samsung devices were previously thought to be immune from Meltdown but the researchers found the open security flaw that they say can be used to spy on users. “There are potentially even more phones affected that we don’t know about yet,” researcher Michael Schwarz told Reuters. “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.” A Samsung spokeswoman declined to say how many Galaxy S7s were vulnerable to Meltdown attacks but said: “Samsung takes security very seriously and our products and services are designed with security as a priority.” The Galaxy S7 is used by some 30 million people.