Project Hyphae

A Quick look at OAuth Permission Attacks

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In the ever-evolving world of cybersecurity, phishing campaigns persist as a serious menace, constantly devising new strategies to exploit unsuspecting individuals. Among their array of malicious tactics lies a particularly cunning approach: the manipulation of OAuth permissions within third-party applications. By tricking users into granting excessive access rights, attackers gain unauthorized entry to critical resources such as emails, calendars, and cloud storage. Part of the real appeal of this technique for attackers is its ability to bypass multi-factor authentication (MFA/2FA) which has, finally, been quite widely adopted.

Originally, OAuth was designed to streamline user authorization for third-party apps on platforms such as Google Apps, Scripts, and Azure Apps. But, as they love to do, cyber criminals have figured out how to use it if for their own nefarious activities. With this newfound weapon, attackers can infiltrate users’ digital lives, setting their sights on valuable assets ripe for exploitation.

OAuth permission attacks have gained some notoriety as of late, showcasing the malicious ingenuity of hackers. By employing sophisticated social engineering techniques, such as deceptive emails and fraudulent websites, attackers exploit the trust users place in well-established platforms. Victims are lured into granting access to their digital assets, unknowingly compromising their security. These attackers are driven by the desire to gain unauthorized access to sensitive data that holds significant value.

These attacks ingeniously exploit legitimate authorization processes, leveraging Google or Microsoft’s own authentication systems, which often include robust multi-factor authentication (MFA/2FA) mechanisms. As a result, even users who have diligently enabled MFA/2FA can unknowingly fall victim to these deceptive tactics, leaving their sensitive data exposed. Attackers set their sights on various valuable resources, including, but not limited to:

  • Emails: By gaining unauthorized access to email accounts, attackers can extract sensitive information, intercept communications, and launch further phishing attacks.
  • Calendars: Access to calendars can provide insights into users’ schedules, allowing attackers to gather intelligence for potential targeted attacks or social engineering tactics.
  • Cloud Storage: Attackers aim to infiltrate cloud storage services such as OneDrive or GoogleDrive to access confidential files or proprietary information.
  • Collaboration Tools: OAuth permission attacks may target collaboration platforms like Microsoft Teams or Google Workspace, enabling attackers to eavesdrop on conversations, extract sensitive documents, or spread malware within shared environments.

The consequences of falling prey to OAuth permission attacks can be severe, with attackers leveraging the acquired access to commit further acts of fraud, data breaches, or identity theft. Organizations and individuals must remain vigilant, implementing robust security measures to protect these valuable assets from falling into the wrong hands.


  • Foster user awareness and comprehensive education on OAuth permission attacks, emphasizing the importance of careful review and verification of application legitimacy, and the access being requested, before granting requested permissions.
  • Conduct routine security audits to meticulously examine cloud platform applications, identifying unknown or unapproved permission grants. Revoke excessive permissions and enforce a “least privilege” approach to minimize the risk posed by compromised applications.
  • Consider restriction on user ability to grant permissions directly to web apps, instead implementing a workflow that requires administrator review and approval for granting permissions.

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