Researchers from CyberArk today outlined a vulnerability they discovered this fall in some Microsoft OAuth 2.0 applications that could allow an attacker to hijack Azure accounts. Microsoft fixed the flaw late last month.
The weaknesses lie in OAuth settings in Microsoft's Portfolios, O365 Secure Score, and Microsoft Service Trust applications, and could be abused by an attacker to grab admin accounts and basically "own" Azure accounts. OAuth is a popular authorization protocol that allows users to share information about their accounts among third-party applications and websites.
"The OAuth applications trust domains and sub-domains are not registered by Microsoft, so they can be registered by anyone (including an attacker). These apps are approved by default and are allowed to ask for 'access_token,'" CyberArk said in a blog post about the vuln. "The combination of these two factors makes it possible to produce an action with the user's permissions – including gaining access to Azure resources, AD resources and more."
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