Security Market Segment LS
Wednesday, 08 September 2021 09:45

Microsoft hit by 20th zero-day attack this year, no patch for flaw yet Featured

Microsoft hit by 20th zero-day attack this year, no patch for flaw yet Pixabay

Microsoft has revealed details of another zero-day attack on its Office software, releasing an advisory prior to issuing a patch for the flaw.

"Microsoft is investigating reports of a remote code execution vulnerability in MSHTML that affects Microsoft Windows," the company said in the advisory issued on Tuesday US time.

"Microsoft is aware of targeted attacks that attempt to exploit this vulnerability by using specially-crafted Microsoft Office documents."

Veteran security reporter Ryan Naraine said of 62 zero-days this year, 20 had targeted Microsoft's products. "This is the 62nd confirmed zero-day attack documented so far in 2021," he wrote. "According to data tracked by SecurityWeek, 20 of the 62 zero-days targeted code from Microsoft."

The advisory said: "An attacker could craft a malicious ActiveX control to be used by a Microsoft Office document that hosts the browser rendering engine. The attacker would then have to convince the user to open the malicious document.

"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."

The default account on any Windows installation always has full admin rights as this is the way the system is set up.

The advisory continued: "Microsoft Defender Antivirus and Microsoft Defender for Endpoint both provide detection and protections for the known vulnerability. Customers should keep anti=malware products up to date.

"Customers who utilise automatic updates do not need to take additional action. Enterprise customers who manage updates should select the detection build 1.349.22.0 or newer and deploy it across their environments. Microsoft Defender for Endpoint alerts will be displayed as: 'Suspicious Cpl File Execution'."

Microsoft said that there was no patch available at the moment to fix the issue, adding "Upon completion of this investigation, Microsoft will take the appropriate action to help protect our customers. This may include providing a security update through our monthly release process or providing an out-of-cycle security update, depending on customer needs."

As mitigation, the company said: "Disabling the installation of all ActiveX controls in Internet Explorer mitigates this attack. This can be accomplished for all sites by updating the registry. Previously-installed ActiveX controls will continue to run, but do not expose this vulnerability."

An additional mitigation, it said, was that, "by default, Microsoft Office opens documents from the Internet in Protected View or Application Guard for Office both of which prevent the current attack."

But as British infosec expert Kevin Beaumont pointed out in a tweet: "To contextualise this, Protected View also protects against macros.. which are the single biggest source of malware in the security industry, as 'Enable Content' in the UI disables it.

"Application Guard for Office is an E5 only feature and isn’t used to open docs by default."

Subscribe to ITWIRE UPDATE Newsletter here


The much awaited iTWire Shop is now open to our readers.

Visit the iTWire Shop, a leading destination for stylish accessories, gear & gadgets, lifestyle products and everyday portable office essentials, drones, zoom lenses for smartphones, software and online training.

PLUS Big Brands include: Apple, Lenovo, LG, Samsung, Sennheiser and many more.

Products available for any country.

We hope you enjoy and find value in the much anticipated iTWire Shop.



iTWire TV offers a unique value to the Tech Sector by providing a range of video interviews, news, views and reviews, and also provides the opportunity for vendors to promote your company and your marketing messages.

We work with you to develop the message and conduct the interview or product review in a safe and collaborative way. Unlike other Tech YouTube channels, we create a story around your message and post that on the homepage of ITWire, linking to your message.

In addition, your interview post message can be displayed in up to 7 different post displays on our the site to drive traffic and readers to your video content and downloads. This can be a significant Lead Generation opportunity for your business.

We also provide 3 videos in one recording/sitting if you require so that you have a series of videos to promote to your customers. Your sales team can add your emails to sales collateral and to the footer of their sales and marketing emails.

See the latest in Tech News, Views, Interviews, Reviews, Product Promos and Events. Plus funny videos from our readers and customers.


Sam Varghese

Sam Varghese has been writing for iTWire since 2006, a year after the site came into existence. For nearly a decade thereafter, he wrote mostly about free and open source software, based on his own use of this genre of software. Since May 2016, he has been writing across many areas of technology. He has been a journalist for nearly 40 years in India (Indian Express and Deccan Herald), the UAE (Khaleej Times) and Australia (Daily Commercial News (now defunct) and The Age). His personal blog is titled Irregular Expression.

Share News tips for the iTWire Journalists? Your tip will be anonymous




Guest Opinion

Guest Reviews

Guest Research

Guest Research & Case Studies

Channel News