Microsoft has patched a subdomain takeover vulnerability in Microsoft Teams that affects every user who uses the Teams desktop or web browser version.

Microsoft Teams is a leading communication and collaboration platform that combines workplace features such as chat, video meetings, file storage, collaboration on files, and integration with applications.

Microsoft Teams Vulnerability

Researchers from CyberArk discovered a worm-like vulnerability that lets hackers use a malicious GIF file to scrape user data and to take over the entire roster of Teams accounts.

The vulnerability resides in how the application programming interfaces (APIs) used to validate the communication between the client and the server.

With Teams access token (auth token) and the skype token is used to make API calls that let users send messages, read messages, create groups, add new users or remove users from groups, change permissions in groups, etc.

According to CyberArk, the following subdomains are vulnerable to takeover;

• aadsync-test.teams.microsoft.com
• data-dev.teams.microsoft.com

An attacker can force the user to visit one of the sub-domains and get access to the auth token, by having the auth token attackers can steal the victim’s Teams account data.

“We considered this approach as well, sending an image to our victim with an “src” attribute set to the compromised sub-domain via Teams chat. When the victim opens this message, the victim’s browser will try to load the image and this will send the auth token cookie to the compromised sub-domain, “reads Cyberark blog post.

Victims will not have any indication of they’ve been attacked as the take over process is stealthy and dangerous.

Researchers published a video POC exploit of the vulnerability, they also warned that the vulnerability is wormable.

The vulnerability has been reported by Microsoft Security Research Center and Microsoft fixed the vulnerability by deleting the misconfigured DNS records of the two subdomains.

A Couple of days before a new Zoom flaw lets hackers record Zoom meeting sessions and to capture the chat text without the knowledge of meeting participants’ even though host disables recording option for the participants.

Due to this COVID-19 pandemic situation, many companies moved to full-time remote work, vulnerabilities like this may pose a huge risk.

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