- Proofpoint reports phishing surge abusing Microsoft OAuth 2.0 device code flow
- Victims enter codes on real Microsoft domains, granting attackers access tokens
- Proofpoint advises blocking device code flows
Cybercriminals, including state-sponsored threat actors, are increasingly abusing Microsoft’s OAuth 2.0 device code authentication flow to take over Microsoft 365 accounts.
This is according to a new report by cybersecurity researchers Proofpoint. In a new paper published on December 18, researchers confirm that have seen a sharp escalation of social engineering attacks since September 2025, in which victims are tricked into granting access to their accounts.
The attack usually starts with a phishing email containing either a link or QR code. Victims are then told that in order to view the contents, they need to reauthenticate their account by entering a device code into Microsoft’s login page.
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Once they enter the code, the threat actors receive an access token tied to their account, not only giving them access, but enabling email monitoring, lateral movement, and more.
The login happens on a real Microsoft domain, Proofpoint further explains, which means that traditional phishing defenses and user awareness checks are mostly useless. The attackers aren’t actually stealing passwords, or MFA codes, so no alarms are triggered there, either.
Proofpoint says there are multiple groups currently abusing this technique, including TA2723 (a financially motivated threat actor), UNK_AcademicFlare (a Russian state-sponsored threat actor targeting government and military email accounts for cyber-espionage purposes), and multiple groups from China.
It was also said that the criminals are using different phishing frameworks, such as SquarePhish 2 and Graphish, which automates device code abuse, supports QR codes, and integrates with Azure app registrations. This lowers the barrier to entry and allows even low-skilled threat actors to engage in attacks.
Proofpoint believes the abuse of OAuth and device code authentication is likely to grow, especially as organizations adopt paswordless and FIDO-based authentication and recommends blocking device code flows via Conditional Access where possible.
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