Windows users are being urged to download an update after Microsoft fixed a bug that had existed in every iteration of the operating system since Windows 95.
Discovered by IBM researchers in May, the bug—called WinShock by some—affected Windows as well as Office products, allowing attackers to remotely control a PC, most likely to then download malicious software to the machine. According to IBM researcher Robert Freeman, the bug was “sitting in plain sight.”
The bug is also said to have the ability to affect secure transfer data software like Microsoft’s Schannel.
The bug was graded as a 9.3 out of 10 on the Common Vulnerability Scoring System (CVSS), according to the BBC.
The researchers stated that while the bug had not been seen “in the wild,” now that it had been made public, it would not be strange to see attacks by hackers on older machines without the software patch.