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Microsoft has fixed a subdomain takeover vulnerability in its collaboration platform Microsoft Teams that could have allowed an inside attacker to weaponized a single GIF image and use it to pilfer data from targeted systems and take over all of an organization’s Teams accounts.

The attack simply involved tricking a victim into viewing a malicious GIF image for it to work, according to researchers at CyberArk who also created a proof-of-concept (PoC) of the attack.

Microsoft neutralized the threat last Monday, updating misconfigured DNS records, after researchers reported the vulnerability on March 23.“Even if an attacker doesn’t gather much information from a [compromised] Teams’ account, they could use the account to traverse throughout an organization (just like a worm),” wrote Omer Tsarfati, CyberArk cyber security researcher, in a technical breakdown of its discovery Monday. “Eventually, the attacker could access all the data from your organization Teams accounts – gathering confidential information, competitive data, secrets, passwords, private information, business plans, etc.”

The attack involves malicious actors being able to abuse a JSON Web Token (“authtoken”) and a second “skype token”. The combination of these two tokens are used by Microsoft to allow a Teams user to see images shared with them – or by them – across different Microsoft servers and services such as SharePoint and Outlook.
 
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