Microsoft has released security updates with the June 2022 cumulative Windows Updates to address a critical Windows zero-day vulnerability known as Follina and actively exploited in ongoing attacks.

“Microsoft strongly recommends that customers install the updates to be fully protected from the vulnerability. Customers whose systems are configured to receive automatic updates do not need to take any further action,” Microsoft said in an update to the original advisory.

“Microsoft recommends installing the updates as soon as possible,” the company further urged customers in a post on the Microsoft Security Response Center.

The Windows 11 22H2 (Sun Valley 2) RTM build 22,621 has resurrected an old bug whereupon a system gets a “hardware security not supported” message even on PCs that meet the necessary requirements.

“After public knowledge of the exploit grew, we began seeing an immediate response from a variety of attackers beginning to use it,” says Tom Hegel, senior threat researcher at security firm SentinelOne. He adds that while attackers have primarily been observed exploiting the flaw through malicious documents thus far, researchers have discovered other methods as well, including the manipulation of HTML content in network traffic.

“While the malicious document approach is highly concerning, the less documented methods by which the exploit can be triggered are troubling until patched,” Hegel says. “I would expect opportunistic and targeted threat actors to use this vulnerability in a variety of ways when the option is available—it’s just too easy.”

The vulnerability is present in all supported versions of Windows and can be exploited through Microsoft Office 365, Office 2013 through 2019, Office 2021, and Office ProPlus. Microsoft’s main proposed mitigation involves disabling a specific protocol within Support Diagnostic Tool and using Microsoft Defender Antivirus to monitor for and block exploitation.