Security Experts:

Connect with us

Hi, what are you looking for?



Microsoft Disables MSIX Protocol Due to Abuse by Malware

Microsoft announced on Friday that the ms-appinstaller protocol for MSIX has been disabled temporarily due to the fact that it has been abused by malware.

Microsoft announced on Friday that the ms-appinstaller protocol for MSIX has been disabled temporarily due to the fact that it has been abused by malware.

Microsoft in December informed users about CVE-2021-43890, which it described as a Windows AppX installer spoofing vulnerability. The tech giant warned at the time that cybercriminals had been exploiting the vulnerability using specially crafted packages to deliver Emotet, TrickBot and Bazaloader (BazarLoader) malware.

Microsoft announced patches and workarounds in December, but it’s still working to address the vulnerability and, in the meantime, it has decided to disable the protocol.

While Microsoft’s announcement suggests that the protocol has been disabled only now, developers complained about it being disabled in December, shortly after CVE-2021-43890 was disclosed.

MSIX is an app package format designed to make it easy for users to install apps and keep them updated. The ms-appinstaller protocol handler enables users to install an application simply by clicking a link on a website, without the need to download the full MSIX package.

Cybercriminals have been abusing this method to deliver their malware to users by tricking them into installing apparently-legitimate applications.

With the protocol handler disabled, the App Installer component in Windows will no longer be able to install an application directly from a web server. Users will have to download the app they want and then install the package.

“We recognize that this feature is critical for many enterprise organizations,” said Microsoft’s Dian Hartono. “We are taking the time to conduct thorough testing to ensure that re-enabling the protocol can be done in a secure manner. We are looking into introducing a Group Policy that would allow IT administrators to re-enable the protocol and control usage of it within their organizations.”

Those who have used the protocol will need to update the application link on their website.

Related: Threat Actors Abuse MSBuild for Cobalt Strike Beacon Execution

Related: Threat Actor Abuses Microsoft’s WHCP to Sign Malicious Drivers

Related: Emotet Using TrickBot to Get Back in the Game

Written By

Eduard Kovacs (@EduardKovacs) is a contributing editor at SecurityWeek. He worked as a high school IT teacher for two years before starting a career in journalism as Softpedia’s security news reporter. Eduard holds a bachelor’s degree in industrial informatics and a master’s degree in computer techniques applied in electrical engineering.

Click to comment

Expert Insights

Related Content


Zendesk is informing customers about a data breach that started with an SMS phishing campaign targeting the company’s employees.


The release of OpenAI’s ChatGPT in late 2022 has demonstrated the potential of AI for both good and bad.

Mobile & Wireless

Technical details published for an Arm Mali GPU flaw leading to arbitrary kernel code execution and root on Pixel 6.

Mobile & Wireless

Apple rolled out iOS 16.3 and macOS Ventura 13.2 to cover serious security vulnerabilities.

Cloud Security

VMware vRealize Log Insight vulnerability allows an unauthenticated attacker to take full control of a target system.

Mobile & Wireless

Apple’s iOS 12.5.7 update patches CVE-2022-42856, an actively exploited vulnerability, in old iPhones and iPads.

Malware & Threats

Microsoft plans to improve the protection of Office users by blocking XLL add-ins from the internet.


A new study by McAfee and the Center for Strategic and International Studies (CSIS) named a staggering figure as the true annual cost of...