There is an in-the-wild exploit for Microsoft Office. A patch has been released. This exploit has turned up on Virtus Total today.
A remote code execution vulnerability exists in Microsoft Office software when the software fails to properly handle objects in memory. An attacker who successfully exploited the vulnerability could run arbitrary code in the context of the current user. If the current user is logged on with administrative user rights, an attacker could take control of the affected system. An attacker could then install programs; view, change, or delete data; or create new accounts with full user rights. Users whose accounts are configured to have fewer user rights on the system could be less impacted than users who operate with administrative user rights.
Exploitation of the vulnerability requires that a user open a specially crafted file with an affected version of Microsoft Office software. In an email attack scenario, an attacker could exploit the vulnerability by sending the specially crafted file to the user and convincing the user to open the file. In a web-based attack scenario, an attacker could host a website (or leverage a compromised website that accepts or hosts user-provided content) containing a specially crafted file designed to exploit the vulnerability. An attacker would have no way to force users to visit the website. Instead, an attacker would have to convince users to click a link, typically by way of an enticement in an email or instant message, and then convince them to open the specially crafted file.
Microsoft has made a bit of a boo-boo this week. Hopefully, you haven’t auto approved patches this week.
KB4041691 and KB4041676 were pushed as delta updates through WSUS. First published on Twitter, but now there is a Reddit thread on the issue https://www.reddit.com/r/sysadmin/comments/75o0oq/windows_security_updates_broke_30_of_our_machines/
If you run into this issue, you will need to boot into WinRE and use DISM to remove the update.
With all updates from Microsoft lately, I recommend you lab them first. Don’t take the risk.