Microsoft is releasing a security update for Internet Explorer that closes a gap that allowed attackers to take complete control of a computer.
It also issued the update to Windows XP users, despite dropping support for the older operating system last month.
Adrienne Hall, general manager of Microsoft Trustworthy Computing, said the company had decided to fix the problem quickly for all customers, saying it takes the security of its products “incredibly seriously”.
Microsoft reported the problem on Saturday, saying it was aware of “limited, targeted attacks” and that the vulnerability affected Internet Explorer versions 6 to 11.
The company said users with automatic updates enabled do not need to take any action.