Microsoft's August security update fixes over 400 issues, including one that attackers had already found and used before a fix was available.

• What it is: This month's Windows update addresses more flaws than usual, including a serious one that was being actively used by attackers against a small number of organisations before Microsoft released a fix.
• Who is affected: Any Windows device that has not yet installed the August security update.
• What the risk is: Devices left unpatched remain open to the issue attackers were already taking advantage of, as well as the other flaws fixed this month.
• What action is needed: Install the August Windows updates without delay. Given the scale of this release, we suggest treating it as a priority rather than waiting for a routine cycle.

We recommend confirming all business devices have applied this update this week.