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Russian-linked threat actor UTA0352 targeted NGOs with Microsoft 365 OAuth phishing that impersonated trusted Microsoft first-party applications, including Visual Studio Code and Microsoft Authentication Broker. The operation sought authorization codes that could be exchanged for Microsoft Graph access tokens; one observed path used Authentication Broker and the Device Registration Service to obtain a refresh token, register an attacker-controlled device, and mint a Microsoft Entra ID Primary Refresh Token (PRT).
A PRT is a long-lived, device-bound Entra credential used to provide SSO and obtain tokens for multiple cloud applications. If attackers gain code execution or access to an authenticated Azure AD/Entra-joined Windows user context, they may be able to request PRT-derived token material through BrowserCore.exe and obtain reusable refresh tokens that can preserve MFA and device-compliance claims. Defenders should correlate Entra sign-in, audit, and Microsoft Graph logs for session IDs reused from different IP addresses, anomalous Authentication Broker-to-Device Registration Service token activity, scripted device registrations, and refresh-token-to-PRT transitions; endpoint telemetry should also flag suspicious BrowserCore.exe and Microsoft account token-provider activity.
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3 events from the most recent confirmed update back to the earliest known activity.
The campaign operators used captured OAuth material and ROADtools to obtain tokens, download Outlook email, and access SharePoint resources through Microsoft Graph. In the device-registration path, they obtained refresh-token material, registered an Entra ID device, and minted a PRT for persistent access; Volexity reported a victim's 2FA approval was followed by email access through SharePoint.
Russian-linked threat actor UTA0352 targeted NGOs with customized Microsoft Entra ID OAuth authorization URLs that impersonated trusted Microsoft first-party applications, harvesting authorization codes and security tokens.
Microsoft Entra ID stopped allowing Primary Refresh Token (PRT) cookies to be requested without an SSO nonce, preventing the previously described nonce-less cookie workflow.
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Threat actors are increasingly abusing **OAuth** in *Microsoft Entra ID* and *Microsoft 365* to obtain **access/refresh tokens** that provide durable access even when passwords are reset and MFA is enabled. Reported activity includes both (1) **malicious OAuth app** registrations and deceptive consent prompts that masquerade as legitimate “business integrations,” and (2) abuse of the **OAuth 2.0 Device Authorization Grant** (device code flow) where victims authenticate on Microsoft’s legitimate device login portal, making the intrusion harder to detect with credential-focused controls. Multiple reports describe campaigns targeting business users and organizations (including technology, manufacturing, and financial sectors) to access resources such as **Outlook, Teams, and OneDrive** and to enable mailbox actions and data access under seemingly legitimate application activity. Research and incident reporting highlight that attackers can persist via **service principals** created in victim tenants after consent is granted, and that some integrations may remain effective even if the consenting user is later disabled; separate reporting also describes **device-code vishing/phishing** that leverages legitimate Microsoft OAuth client IDs and standard login workflows to capture tokens without attacker-hosted phishing pages, with one source attributing the vishing activity to **ShinyHunters** (unconfirmed by Microsoft at the time of reporting).
Jun 29, 2026
A phishing campaign abused Microsoft's OAuth 2.0 **Device Authorization Grant** (`Device Code Flow`) to capture valid Microsoft account tokens without sending victims to a counterfeit login page. Victims received emails posing as legal notifications, including password-protected PDF attachments, and were funneled through phishing pages that displayed a one-time device code before directing them to the legitimate `microsoft.com/devicelogin` page. After victims entered the code and completed normal MFA on Microsoft's real site, the attackers obtained `access_token`, `refresh_token`, and `id_token` values tied to attacker-controlled applications. The stolen tokens enabled persistent access to Microsoft services including **email, OneDrive, and Teams**, allowing attackers to read messages, access files, and monitor conversations. Researchers said the activity was observed from early April to mid-May 2026 and included a Brazil-focused variant that used legitimate redirect links, including on **cacoo.com**, to add credibility to the lure chain. Defenders were urged to reject unexpected device authorization prompts, inspect redirect parameters in otherwise legitimate URLs, disable Device Code Flow in Microsoft Entra ID where it is not needed, and monitor **DeviceCodeSignIn** and anomalous sign-in activity for signs of compromise.
Jul 9, 2026
Researchers and incident responders are warning that attackers are increasingly abusing Microsoft Entra ID's OAuth 2.0 **device code flow** to hijack Microsoft 365 accounts through legitimate sign-in prompts rather than malware or software exploits. In these attacks, victims are tricked via **vishing** or phishing into entering an attacker-supplied code at Microsoft's device login page and approving MFA, which issues the attacker valid access and refresh tokens. Security firms say the technique can provide broad access to services including **Microsoft Graph**, **Exchange Online**, **OneDrive**, and **SharePoint**, and that password resets alone may not fully contain the intrusion because refresh tokens can persist across services. The activity has been tied to data theft and follow-on abuse. ReliaQuest reported that the **Helix** extortion group used device code phishing, MFA abuse, and rogue authenticator registration to access victim Microsoft 365 tenants, enumerate SharePoint, and exfiltrate data before extortion; reported victims include Medtronic, Nissan, NAIC, Kodak, Infinite Campus, and the University of Nottingham. Separate investigations documented attackers signing in from foreign locations, registering multiple devices, creating hidden inbox rules to suppress replies, and using compromised mailboxes to send phishing messages at scale. Microsoft and security researchers recommend blocking or restricting device code authentication with **Conditional Access**, limiting SharePoint and device registration to managed devices, and monitoring Entra ID telemetry for `AuthenticationProtocol` set to device code, unusual travel, mailbox rule changes, and spikes in device registrations.
Jul 23, 2026